The Redskins and Cowboys will find out this evening at RFK stadium what they are worth on a football field.

What they are worth to their owners' bank accounts is another question.

If a good National Football League team such as the Redskins or the Cowboys were for sale today, the asking price would be likely to exceed $30 million, according to authoritative league sources.

In return, a buyer would receive celbrity status, the psychological rewards of being in the owner's box and lucrative tax breaks.

But the annual income from such a team wouldn't provide much to cheer about, present owners of major teams insist.

From the financial point of view, the Redskins probably did no better in 1979 than the last place Green Bay Packers, the only NFL team that issues a public financial report. That means an after-tax profit of less than $1 million last year, league sources say.

Like diamonds or rare works of art, the Redskins and Cowboys may be fun to look at but won't make their owners rich -- unless they are sold. m

If owner Jack Kent Cooke ever tired of the Redskins and sold out, he would be consoled by the incredible appreciation of his initial investment. Nineteen years ago, Cooke and a partner purchased 25 percent of the Redskins' stock for a reported $350,000, or $1,521 a share. Today Cooke owns 85.7 percent of the Redskins stock: If the team is worth $30 million, his 300 shares would be worth $85,714 apiece

How much football team owners make and how much they are worth isn't public, of course, because stock in major teams is privately held by a very few owners who don't talk about profits, particularly within earshot of their players' attorneys. The profit and loss sheet is a sanctum sanctorum.

But some educated assumptions can be made by inspecting the financial reports of the Packers, a publicly owned team that is obliged to publish them.

Like other NFL teams, the Packers last year had two chief income sources: ticket sales and their share of the league's contracts with television networks that broadcast the games. These are the figures: Green Bay Packers Income

$5.8 million from television, radio and program sales receipts

$1.9 million net income from regular season home games

$1.4 million net from out-of-town contests

$783,456 from pre-season games

$10,044,559 total income from operations Expenses

$5.3 million for salaries of players, coaches and front-office personnel

$2.5 million for operating expenses including travel, equipment and overhead

$8,063,492 total expenses from operations

$1,981,107 profit from operations before taxes

League sources say the Packers are among the NFL's more profitable teams and that the Redskins would be lucky to do that well.

To the NFL Players' Association, this sounds like poor mouthing by the owners in preparation for the next round of contract negotiations. Richard Berthelsen, association general counsel, is skeptical that the Packers' financial report reflects the pattern around the league generally.

For all teams, salaries represent the biggest single expense.

A survey by The Washington Post last November reported that the Redskins had cut their player payroll in 1979 by about $200,000 from the high of $3.6 million reached in 1977 under coach George Allen. That year, the team could field a backfield including Billy Kilmer, John Riggins, Mike Thomas and wide receiver Charley Taylor, whose combined salaries exceeded three quarters of a million dollars.

The current Redskins are younger -- and less well-paid. But the Redskins still are making deferred salary payments to retirees from the Allen era. John Riggins, for example, has $800,000 in deferred salary coming over a period of years.

According to league sources, the Redskins, once the leader in player salaries, had dropped into the middle of the pack last season, behind the Pittsburgh Steelers, Oakland Raiders and New England Patriots. They probably are still ahead of the Packers.

Counting coaches and front-office salaries, the Redskins' payroll was about $5.2 million last year, according to The Post survey -- on a par with the Green Bay Packers.

Another major expense is stadium rental. The D.C. Armory Board, which rents RFK to the Redskins, refuses to discuss the contract terms. Fours years ago, The Washington Post obtained team financial statements showing stadium expenses of $701,826 in 1975. One league source said the Redskins' rental costs are on the high side compared with the other, younger clubs.

The Redskins also pay interest charges on loans used to purchase stock from the estate of the team's former owner, George Preston Marshall. Interest charges totaled $840,733 four years ago.

Ticket sales provide the largest income source for most clubs, including the Redskins. A survey by the Green Bay Packer organization showed that the Redskins had the second-highest average ticket price in the league last year -- $12.46. Multiply that by the seating capacity at RFK (55,031), and the result is a sell-out revenue of $685,518 per game. That produces $6.8 million for 10 home games.

The Cowboys' average ticket price was $9.75 in 1979, according to the Packer survey, but the greater capacity of their home stadium brings in a sell-out revenue of $634,430.

The second major source of income is the television networks. Each NFL team receives the same amount from the networks, from the proud Steelers to the once-proud Packers.

The teams share $23 million over a four year contract that still has one year to run. The amount rises each year, from an initial $4.9 million to about $5.5 million this year, according to league sources.

The Redskins financial statements from four year ago show a meager after-tax return. The team earned $82,544 in 1973, the year of the Super Bowl. A $340,463 was reported in 1975, due in part to a player strike that hurt attedance.

As Berthelsen figures it, the Redskins should be much more profitable today. Television revenue last year was more than twice the $2.3 million received in 1975, while total player compensation has risen much less, from about $3.2 million to close to $4 million, including bonuses.

League sources say otherwise. Assume that the Redskins made half of what the Packers earned on football operations last year, after taxes -- the return would be about $800,000, a miniscule amount on an investment probably worth $30 million.

But the multimillionaires like Cooke, the Redskins majority owner, and Clint Murchison, who owns the Cowboys, aren't in the game for the annual income, says Les Silverstone, an investment counselor who heads the Washington office of Dean Witter Reynolds.

"Nine-tenths of the owners would give up the money to win," Cowboys President Tex Schramm said in a recent interview. "People are not in football for the money. You've got to have money to afford to be in it."

Murchison says it took the Cowboys five years to make a profit. "We lost something in the neighborhood of $3 million before we began making money around 1965. But since 1966, the profits of the Cowboys have not increased," he said in an interview in Texas Business magazine.

"the truth of the matter," he added, "is that football is not highly profitable because it's not a growth business. There are just so many tickets we can sell, and that's it. The only real growth you have is the TV revenue, and much of that floats down to the players, as it should."

What grows dramatically is not the annual profit but the value of the team to wealthy would-be owners.

Murchison paid only $50,000 for the Dallas franchise in 1960, doling out another $550,000 for players drafted from other teams. He says the franchise is worth $17 million, a figure that strikes some league sources as far too conservative.

Cooke, who in the 1930s started out peddling encyclopedias in Canada during the Depression, was a millionaire by 1943. He entered the Redskins' picture in 1961, joining with another investor to buy a one-quarter share of the team for a reported $350,000.

After a series of stock purchases, Cooke now owns 85.7 percent of the Redskins stock -- 300 shares. The remaining 50 shares are owned by Edward Bennett Williams, team president.

Value of the Redskins stock has soared in the past two decades, as professional football established itself as a national pastime. The stock was valued by an outside appraisal firm at $11,141 a share in 1971. Three years later, when Cooke was said to be looking to sell, the asking price was reportedly $45,000 a share, too high for potential buyers then.

But that price presumably wouldn't be an obstacle now.

"If the Redskins only broke even, it still wouldn't affect their value," says Les Silvestone. "It's a hot potato. Somebody will always pay more than what you paid."