Corporate America has opened its checkbooks and its warehouses for President Reagan's inaugural committee, supplying everything from millions of dollars in interest-free loans to four tons of M&Ms and a fleet of white Chryslers "like the ones Ricardo Montalban advertises on TV."

But inaugural planners are not just relying on corporate generosity to pay for the nation's 50th inauguration, one that they hope will cost far less than the record-breaking $16-million price tag for the festivities four years ago.

They have taken a lesson from their big-business friends and, for the first time, are hawking inaugural souvenirs in special boutiques at Bloomingdale's and Saks.

"We are going to run this like a business," inaugural chairman Ron Walker vowed in December, and indeed they have.

"I got the feeling that they're not exactly doing this for altruistic reasons," said one buyer who negotiated with the Reagan marketing team. "They're in this to make some money."

As far back as planners can remember, inaugurations have cost money and have paid the bills themselves, but never before has the marketing been so sophisticated nor the corporate largesse so great as this time under the free-enterprise presidency of Ronald Reagan.

Last November, when the inaugural committee threw open its doors, it needed $8 million in interest-free loans -- "seed money," planners said -- to get the operation going until ticket and souvenirs sales could put it in the black.

"We put out the word to likely donors," said committee spokesman Jim Lake. "It was first come, first served, y'all come."

In 12 days, the committee met its goal.

"We had to say 'No, thank you' to about two or three million dollars," Lake said. "We didn't want to raise more than we needed."

The list of lenders, released yesterday, reads like the Fortune 500 listing and then some: from Dow Chemical to General Motors and from oil companies to pharmaceutical firms, along with a sprinkling of the trade associations that lobby for everyone from builders to bankers to broadcasters in the nation's capital.

Such corporate involvement has come under some criticism.

"I think it's unbecoming for the administration to blatantly finance its inaugural activities with private contributions from business corporations who certainly expect some return favors," said Joan Claybrook, president of Public Citizen, the consumer advocacy group that Ralph Nader started.

The cost, she said, seems more befitting "a coronation" than a presidential swearing-in.

"She does not seem to be entering the spirit of the nation inaugurating a president every four years," inaugural spokesman John Buckley responded. "The inaugural committee every four years, be they Democrats or Republicans, conservatives or liberals, seeks to bring off the best inauguration, the kind the country deserves."

The last Democratic inauguration was Jimmy Carter's no-frills 1977 celebration, which cost $3.5 million.

This year the country will be getting a $12-million inauguration, if chairman Walker has his way, with fireworks spectaculars, a "young Americans pageant" and nine inaugural balls.

These events will be paid for from the sale of tickets, which run $125 apiece for inaugural balls; souvenirs that go for anywhere from $5 for a poster to $1,750 for a "limited edition presidential eagle" by Boehm; and the sale of commercial time on a televised "presidential gala" featuring performers such as Frank Sinatra.

We bought 60 seconds of commercial time ," said an Anheuser-Busch spokesman, who added that the spot probably will plug Budweiser and Michelob Light.

Asked if the commercial could be seen as a statement of support for Republican Reagan, the spokesman said: "No. . . . No more than sponsoring the Super Bowl suggests we're rooting for one of the teams."

The committee has sold 13 of the 14 minutes of commercials it has available, at about $300,000 per minute, officials said. But it has not been an easy task.

"Three hundred thousand ain't chicken feed," said inaugural press chief Lake. "The companies want to know, 'Are we getting our money's worth?' "

Sometimes, said Lake, the committee works through its advertising agents and sometimes it gets a little help from friends in high places, whom Lake said he would rather not name.

"We're working at both levels," he said recently. "You don't want to use the big chip all the time."

If the committee knows how to woo new corporate comrades, it also knows how to handle the ones that it has.

"I've been drinking a lot of free Cokes and Pepsis," said Buckley, ever the diplomat. "An equal amount of each."

Along with free soft drinks, Coca-Cola, the Atlanta-based company known for its ties to Jimmy Carter, loaned the committee at least $50,000, and PepsiCo, a longtime Reublican ally, came up at least a $100,000 loan.

But what the committee did not pick up in loans, it got in other ways.

American carmakers, for instance, have provided the committee with more than 360 cars, including the fleet of 43 white Chryslers.

"It's the kind of car Ricardo Montalban advertises on TV," a spokesman said, "when he says 'if you drive a turbo-charged New Yorker, you'll never drive a V-8 again.' "

When the cars need gas, the committee just draws on some of the 17,000 gallons of high-test gasoline that Shell Oil has made available.

The manufacturers say that it is a good deal for them, too, because the cars, which later are sold, gain inaugural cachet.

"Say you're a Beverly Hills Cadillac dealer and a guy comes and wants the car driven by the governor of Alabama," a General Motors spokesman hypothesized. "You can say, 'I've got it right here.' "

Chrysler's spokesman boasted that his cars have been seen around town with their special inaugural plates that say, for example, "Chrysler 10."

"The heads-up people at the inaugural committee thought up that one," he said. "They've done a first-class job."

That, said inaugural marketing chief Douglass Blaser, is precisely what he had in mind.

It was Blaser's brainchild to register the inaugural seal as an offical trademark and then sell the "official commemoratives" in a new way. In the past they have been available only through catalogs, but Blaser's team talked Bloomingdale's, Saks, Hecht's and Woodward & Lothrop into selling them, too.

Hecht's opened its inaugural boutique this week. They are carrying the "official inaugural mint" at $7.50 per package, a $295 Royal Doulton mug shaped like a figure of Ronald Reagan and a limited edition "soaring eagle" that goes for $950, according to spokesman Peggy Disney.

"I think those are already sold out," she added, "believe it or not."

Blaser also is the man behind the plan to license official inaugural foods, and make about $100,000 in the bargain. Thus was born the official inaugural champagne, Korbel, and the official munchie: "Morrow's Inaugural Nibbles."

And what do the corporations get out of all their efforts?

"We do it because we expect favors," joked one corporate spokesman who was quick to add: "Only kidding."

Others said that it was just business as usual.

"You can't say no if all the other manufacturers are doing it," said the spokesman for one auto maker. "They ask for the cars. I don't know of any inaugural that hasn't asked. It's sort of part of their check-off list."

Then again, a donation is not always what it seems.

Buckley said that the committee had gotten "a good deal" on beepers from MCI Communications.

MCI spokesman Gary Tobin did not agree.

"We leased them for . . . $7,500," said Tobin. "Maybe we have great sales people who said, 'Have we got a deal for you.' But, as far as I know, that's the normal price." CAPTION: Picture 1, Phtorgraphers' stand frames work done in preparation for the Jan. 21 presidential inaugural ceremonies on the Capitol's western side. By James K.W. Atherton--The Washington Post; Picture 2, Furied flag forms handle of this Ronald Reagan mug, which has $295 price tag. AP