Readers have reacted to a Washington Monthly Magazine (quoted in part three May 5). It said that Washington feds are misled about ''real world'' pay and finges of private sector types, because the private sector here is a typical of the private sector in most cities.

Other readers have written about the government crusade against thelephone abuse. Here are the letters:

''Your May 5 article with the headline 'Who's Got the Beef?' should have been called 'Who's Got the Needle?' It seems the Washington Monthly magazine will never be content to stop needling federal workers until someone reintroduces the 19th century die-at-your-desk retirement plan!

"You noted that customers at high-priced restaurants are almost never federal workers. The explanation is simple: Federal professionals lunch at the cafeteria because they are too busy to lunch at Le Pavillon or The Palm.

"Who can be productive after a three-martini lunch? Perhaps it is because people in the private sector don't work as hard as government employes that industry can afford the three-hour, three-martini lunch at a luxury establishment. And you know who pays the bill.

"Why compare government lawyers, engineers and accountants with blue-collar workers in Youngstown, Ohio, or Hagerstown, Md. A professional should expect comparable pay and fringe benefits where that person works.

" . . . What you are saying is that we can't beat the system we should join it. You want to cut the size of government by encouraging professionals to leave, join industry and enjoy the benefits of expense account lunches, country club members, higher pay, free retirement benefits and fully paid health insurance." J.E.M., Springfield

"The suggestion that federal workers want higher pay so they can eat at fancy restaurants like fat-cat lawyers and lobbyists is ludicrous. The average house in Alexandria is over $100,000 and you don't get much for that!

"When you pay over $1,000 a month for a mortgage or $700 for rent and combine it with the high taxes in this area that fat salary shrinks dramatically.

"Maybe federal workers don't have a realistic view of the size of private-sector salaries outside Washington. But I don't think our critics have any idea how expensive it is to live here . . . . If you can't afford a place to live, it doesn't make much difference whether you can eat at The Palm! J.B.A., Alexandria

"I read with interest about the May 9 story about the government crackdown on phone abuse.

"The thought came to me that maybe the government should place a sign on the phones, like the warning on franked government postage-paid envelopes. The warning should advise employes of penalties of abusing phone use. I have never seen a federal employe abuse the franked mailing privilege . . . . " -- A Rosemont, Ill., reader

"On the subject of abuse of government facilities . . . I thought I would share with your readers abuse I witnessed for several years. It has to do with travel by government officials to cities where their children are in college.

"One of my bosses used to make regular visits to a U.S. installation near Denver where his son was in college. When his son graduated he never again visited the facility. This is a terrible form of abuse of the taxpayers' dollar.

"Incidentally, this official never visited Denver before his son went to college. Meanwhile, there were many offices that need a visit from him. He never did because he didn't have the time!" Signed, An Honest Fed, one of many