IN HIS WAY, my son, who is seven, is learning about money. He's learning that some things are expensive and some things are not Ice cream something like a car is. A car, especially the four-wheel-drive Jeep that for some reason he wants me to buy, is very expensive. It costs, he thinks something like a million dollars. He is wrong. I think it costs $3,000. I am wrong, too.

Somehow it has happened that we are both wrong about prices most of the time. His excuse is that he is just learning about them. My excuse is that I have already learned. In my head is a checklist of prices. They are the ones I learned when I learned about prices and money, and try as I might I cannot get them out of my head.

A really good house costs $40,000. This is a terrific house, one with an oval driveway and a statue of a jockey holding a lamp right at the doorway. When I buy that house, I will get rid of the jockey, but not the Lincoln car and Julia Meade getting out of it. With the Lincoln and Julia Meade. I'll go as high as $41,900. Not a penny more.

A car costs $3,000. This is what is costs for a really good car. You can get a VW for $1,800 and maybe something like a knock-down Plymouth for two grand - no white walls, of course. This is the price in my head, the one I revert to when I am not thinking. When someone tells me that a car costs $9,000, I am shocked, adjust for awhile, and then revert to the old price.

A haircut costs $1.25 - $1.50 an Saturdays. A suit costs $75 and movies cost 75 cents and a trip to the supermarket costs, on a really big day, $20. A gallon of gas costs 30 cents and a package of cirgarettes, something I no longer buy, costs 25 cents. It's up from 22 cents.

The thing about this sort of thinking is that it costs me money. I will not buy a shirt that costs something like $25 because I think it should cost $14, but I will go out to dinner, thinking for some reason that my wife and I can eat nicley for $12. When I get the bill, I promptly go into shock, remind myself that it now costs a fortune to eat out, and then promptly forget it. I do this every time. I go into shock a lot.

There are some things that no longer have any price. I have no idea of what to tip people anymore. The quarter used to be ubiquitous. You could use it for anything. Someone opens your door, give him a quarter. Someone brings you your car, tip him a quarter. A kid comes with a delivery, give him a quarter. No more. Now I have no idea what I'm supposed to give. Sometimes I give a quarter and sometimes a dollar and sometimes something like 30 cents. Sometimes I just want to ask them what they think they ought to get.

For some things, though, I never did have a price. Cantaloupe is an example of that. For the life of me, I can never remember the price of a cantaloupe. I recently paid $2 for one, knowing that this was high, but not really caring. I need cantaloupe for my diet-the Richard Cohen Eat-Nothing-But-Cantaloupe-Diet-and so I will pay anything for it. This is what will happen with gasoline. The high price of gas will mean nothing. People will pay it since gas to most people is as important as cantaloupe is to me. Soon, America will be like Italy.

In Italy, where gas costs something like $2.50 a gallon, everyone has a car and everyone drives. They drive to work in the morning and they drive home for lunch and then they drive back to work and then they drive home again. It's a crazy system. It pollutes the air and it costs everyone plenty, but this is the way they prefer to do it. They spend all their money on cars and gas and good-looking clothes. Soon, it will be the same here. Maybe the food will also improve.

Back to prices. In my head, chopped meat costs 59 cents a pound and newspapers are a nickel and paperback books are 95 cents and lunch is $2. The shuttle flight to New York is $18, and the cab into town is $4.80. Jeans cost about $8 and everything else in the world costs 79 cents, which used to be, I swear, the price of everything.

There are some things now, though, that have no prices. A visit from a plumber costs anywhere from $20 to $200, the difference being solely a matter of his mood. The same holds for electricians. A single rose costs $1; so does a bouquet of any other flower, and something really terrific for a girlfriend on Valentine's Day costs $3 - delivery included.

In the stores, I buy mostly the store brands, not because the savings are that much, but because I want to teach the major brands a lesson. They cannot take me for granted. Still, I will pay anything for coffee, and most people will pay anything for plastic wrap and Gold knows what the ceiling would be for toilet paper.People will, I'm sure, pay hundreds of dollars some day for a good pair of jeans, and a haircut will cost $50 and a four-wheel-drive Jeep will cost, I'm sure, a million dollars and my son will be right. It won't do him any good, though. At 10, he'll byoung to drive.