PRESIDENT REAGAN was right to reject as insignificant his advisers' suggestions that he raise the excise taxes on cigarettes and booze.

The federal deficit is approaching $100 billion. It is impossible to erase such a deficit with nickel-and-dime taxes on packs of cigarettes.

This nation, as President Reagan said in the closing of his State of the Union message, must "work together to bring America through difficult times." It needs to enact whopping levies on the sale of marijuana.

Americans consume more marijuana cigarettes each year than McDonald's sells hamburgers. Over 20 billion served, the Drug Enforcement Administration estimates. Americans spent at least $25 billion on marijuana in 1980, according to preliminary DEA statistics.

Isn't it time we stop handing over this money to lawbreakers and apply it to a useful social purpose like rescuing Reaganomics?

Isn't it time we stop posturing and start looking in a hard-headed, Republican fashion at the numbers?

Production costs for American marijuana farmers are estimated to be at most the same as those for tobacco growers: about $1 an ounce. If you generously allow a 100 percent profit margin, figure the retail cost to be $2 an ounce. (In Colombia, the supplier for much of the North American drug market, the peasants who grow the stuff get as little as 12 cents an ounce, the DEA estimates.)

The retail price of marijuana in the United States now averages around $40 an ounce, with the price for the finest American-grown product reaching $125 an ounce.

There is obviously a huge margin of profit at every step of the marijuana distribution system, which is why the industry has become so huge despite the fact that it operates completely outside the law.

If marijuana were legalized, it could be sold with a whopping 750 percent tax of 50 cents per cigarette, or about $15 per ounce. This would raise $10 billion dollars a year in federal revenue.

That's the entire amount spent by the federal government on housing for the poor.

The cost to the consumer, meanwhile, would still only be $17 an ounce, less than half the cost of illegal marijuana.

If you wanted to tax it by 1,250 percent, or $25 an ounce, you would get $16 billion a year. That's the entire federal contribution to Aid to Families with Dependent Children (welfare) and food stamps combined. And the price to consumers is still $13 less than the current price.

Any tax on marijuana would have to be set low enough to guard against competition from illicit market sources. But as long as the potential exists to purchase legal marijuana of a superior quality at a low price, marijuana consumers will opt for it over the illicit market. As a matter of fact, American-grown marijuana is the finest in the world today, largely because of America's superior agricultural technology. With the resources of agribusiness research facilities available to a legalized marijuana industry, there is no way that the primitive illegal product from Colombia or elsewhere could compete with the commercial product.

But the "revenue enhancement" is only the tip of the economic advantages generated by the legalization and taxation of marijuana.

Think of the budget cuts available to David Stockman if we would stop the futile attempt to enforce the most widely ignored laws in the country: those meant to prevent the 40 million regular marijuana smokers in the United States from doing so.

Seventy percent of all drug arrests are for marijuana offenses, and nearly 90 percent of those are for possession of small amounts of marijuana, according to statistics gathered by the Federal Bureau of Investigation.

It costs about $25,000 to successfully prosecute a typical marijuana case, and approximately $20,000 each year to incarcerate someone convicted of a marijuana offense.

There are approximately 20,000 persons presently in prison for marijuana offenses. They represent half a billion dollars in prosecution fees, and $400 million a year to keep them locked up. That's almost a billion dollars right there.

Removal of marijuana cases from the criminal justice system would eliminate 400,000 additional cases per year from an already seriously overburdened judicial system.

It would also help alleviate the overcrowding in many of the nation's prisons that is so serious that it has been ruled unconstitutionally cruel and unusual punishment. The low- average cost of a new federal prison cell is $40,000. Multiply that by 20,000 prisoners, and you have another $800 million saved.

The DEA, the FBI, the Coast Guard and the Customs Service have combined budgets of $3.5 billion. What portion of that cost could be eliminated if these agencies no longer had to worry about enforcing marijuana laws?

For that matter, the Forest Service, the Park Service, the State Department and many other federal as well as state and local agencies spend billions of dollars each year trying to confiscate, eliminate, eradicate or otherwise obliterate marijuana from this country.

The Customs Service recently announced that in 1981, it confiscated 3 million pounds of marijuana. The DEA and the Coast Guard also confiscated record amounts. In spite of this, there is no law enforcement official alive who thinks the amount of marijuana confiscated represents even 10 percent of all the marijuana smuggled into the United States in 1981. There is more marijuana available today than ever before.

In addition, there are now 30 states, according to National Organization for the Reform of Marijuana Laws (NORML) estimates, that produce domestic marijuana crops of $100 million or more. Perhaps $8 billion worth of marijuana is grown domestically. If the state of California spent $87 million to spray malathion on medflies last year, think of what it would cost to try to eradicate its $1.5 billion marijuana crop.

The monetary advantages of legalizing and taxing marijuana do not even end with budget savings.

Marijuana is a serious balance-of-trade issue. The Wall Street Journal has speculated that if the multibillion-dollar underground economy were ever taken into account, the United States would be revealed as a net agricultural importing country.

Sam Nunn, former chairman of the Senate Investigations Subcommittee, has said, "These 'narcodollars' (money that flows abroad to buy marijuana and other drugs) may have an economic impact that is similar, in character if not size, to the more infamous 'petrodollars,' both in terms of inflation and on our balance of payments. Every narcodollar that is paid to a Colombian pot grower or hidden away in a numbered foreign bank account is lost to our economy, just like a petrodollar spent for one gallon of imported gasoline." It is likely that marijuana, if it were reported, would be the second leading cause of the American balance of trade deficit, following oil.

Against such compelling tax-increase, budget-decrease and balance-of-trade arguments comes the suggestion that if marijuana were legalized, every 12-year-old in the nation would spend his or her day stoned.

This is obviously no more in the national interest than that every 12-year-old spend his or her day smoking tobacco or sipping bourbon. It is equally unlikely.

Legal regulation of marijuana would offer many similarities to that of alcohol. There would be age restrictions on purchase and use, laws against driving while under the influence, restrictions on public use (i.e. buses, restaurants, etc.) and laws allowing over-the- counter sales only in certain licensed retail establishments (said licenses being yet another source of tax revenue).

Another argument against the legalization and regulation of marijuana is public health. There is no question that smoking marijuana is not harmless. Ingesting anything into your lungs probably isn't good for you, and long- term heavy use undoubtedly has negative health effects.

Yet marijuana used occasionally or in moderation for short periods of time causes no serious health hazards to the user, and what's more, legal regulation would eliminate contaminants from marijuana that moves uninspected through an illicit network. By the time that it is sold on the streets, marijuana has sometimes been contaminated either intentionally or accidentally.

One source of contamination is PCP or other adulterants added to low-quality marijuana for an "extra kick." This tainted marijuana usually is offered to unsuspecting users in high schools and urban inner city neighborhoods and is truly dangerous.

Another source of natural contaminants is bacteria or viruses. More and more reports have surfaced in recent years of people becoming ill after smoking contaminated marijuana. Without a regulated market, there is no means to inspect marijuana growers, much less issue a recall.

The third major source of contamination is paraquat, a herbicide used to eradicate marijuana which can lead to permanent lung injury, according to the Center for Disease Control. Obviously, this chemical would not be used on legal marijuana.

Ironically then, the public health problems associated with marijuana could be lessened after legalization rather than increased. Health problems involving contaminants in bootleg alcohol were one of the reasons for the end of Prohibition.

But back to economics. The question is this: The federal government is now cutting back food, shelter and educational opportunities at an unprecedented rate. All we have to do to alleviate some of this pain is legalize and regulate a "sinful" pleasure regularly engaged in by 40 million Americans, just like we legalized and regulated lotteries to support the elderly or the schools.

Which would you rather have? Unenforceable laws against marijuana or the end to $100 billion deficits?