Amazing policies from the world of commerce, Washington, D.C., division:

Case One, Wolf Trap Farm Park, Vienna, Va. . . . Priscilla Murphy of Alexandria arrived for an evening concert with her 4-month-old son in her arms. She was stopped as she tried to enter the seating area. A ticket taker informed her that every person, no matter how small, must have a ticket.

"Huh?" said Murphy.k

"Policy," said the ticket taker.

"I've seen people bring coolers to Wolf Trap that are bigger than my son," Murphy said the other day on the phone.

"Besides, parents who bring young children all go sit up in 'Siberia' [the top of the lawn seating area] anyway, so they distrub as few people as possible if the kid starts crying.

"I can't believe it."

You'd better start, Priscilla.

"Yes, it is our standard policy," says Suzanne Stephens, Wolf Trap's assistant press director.

We publicize it in all our literature, and we offer a parent the option of a refund if he doesn't know about our policy and gets to the gate and doesn't want to pay for the child.

"Our intention is to provide for the enjoyment of all our patrons. This way, if a patron is disturbed [by a crying child], Wolf Trap can say the child had a right to be there because he paid. . .

"It's not because we're trying to soak the public for all the money we can. And we're not trying to discourage children from coming. You just can't forget that for some of our performances, rapt attention is required."

Case Two, Wolf Trap again. . . Beatrice Black of Arlington gave up driving a few years ago, but for a while, she didn't have to give up Wolf Trap concerts, too. There was a bus that ran directly to Wolf Trap from the Marriott Key Bridge Hotel in Rosslyn.

But two years ago the service died from lack of patronage. As a result, Beatrice Black's attendance did, too.

She went to more than a dozen Wolf Trap concerts in 1979. Last year, she attended one, on the only occasion that she could arrange a ride. This year: none.

"Are they really trying to tell me that there's no public transportation whatsoever to a federal preserve for the arts?" Black asks.

Right again, Suzanne Stephens acknowledges.

"We looked long and hard, but we couldn't find anyone who could make bus service financially feasible," she said.

"I think it's terrible," Stephens offered. "But I'm afraid it's true."

Case Three, Suburban Trust Bank, Rockville branch . . . Diane Plotkin of Rockville was doing errands in the neighborhood when she thought she spied a chance to save time.

The aisles of the bank were clogged with people. But by a fluke, the drive-in window was vacant. Nary a car, motorcycle or bicycle was in sight.

So Diane marched up to cash a check. Whereupon the teller said that a customer who wasn't on wheels of some kind couldn't be accommodated at the drive-in window.

Madness? Nope, policy, explained Janice Stanton, Suburban Trust's public relations manager.

"Our insurance requires us to do this. What if a car drove up and she [on foot] were somehow injured? We can't predict whether someone would step out in front of a car.

"I admit sounds silly, but. . ."

Case Four, Suburban again, Bowie branch . . . John Bonomo of Bowie got it into his head to open a small savings account for each of his grandchildren. iBut he discovered that Suburban charges $2 each quarter to keep alive any account whose balance is less than $100. John immediately began thinking of other ways to be a caring grandfather.

"Unbelievable," said Bonomo. "Let's say you put $100 in an account. They pay you $5.25 a year in interest, but you have to turn around and pay them $8 in fees. So you end up with $2.75 less than you started with.

"Is that the way to explain money to children? That's just arrogance."

No says Stanton. It's business.

"We have expenses like any other business," she said. "Perhaps we drove some small accounts away with the policy [which went into effect April 1, 1980]. We haven't found it's driven away others."