Warsaw flea market: antiques -- and dish detergent

''I thought you were really interested,'' the owner said reproachfully. I was , but not to buy the magnificent harmonium perched atop and dwarfing his little car.

It was a beauty -- woodwork delightfully finished, still in good condition, the keyboard shining black and white.

''It's 200,000 zlotys ($2,500 at the official rate),'' he said, ''but we can discuss that.'' He started to free the veteran instrument from the cords holding it to the car. ''Try it,'' he said.

It was time to retreat. ''But, mister, I told you we would make you a good price. . . .''

This was at Volumen, Warsaw's biggest flea market. It is an extraordinary place where not only antiques and memorabilia from old mansions and attics are on sale, but also many of the goods that are in short supply or absent altogether from the shops are hawked by modest ''entrepreneurs.''

A four-foot-high brass and gilt Russian samovar flashed in the warm June sun. One hundred seventy thousand zlotys, the man said. Topping the samovar was a graceful, conventional teapot. He wouldn't sell it separately, but a price could be agreed on.

The market covers several acres. It was packed with people. A few thousand cars were parked outside.

There was a magnificent cabinet of old, highly worked silver cutlery for a table for 12 -- a reminder of a more spacious age. So were walnut wardrobes and chests of drawers that any auctioneer anywhere would tell you were ''good pieces.''

But contemporary Poland was represented, too. Every few steps, it seemed, there was someone offering a package of detergent, a pack of cigarettes, a few transistor batteries, tubes of shampoo, a cake of soap, a pair of shoes. All these items were ''Western'' and high priced because they are scarce.

There were Western jeans - at 10,000 zlotys (about $125). My assistant was wearing the same brand, bought in the United States for $30. (The average income in Poland is 9,000 to 10,000 zlotys a month, including price compensations.)

There were Western leather handbags and travel bags, some for ''Spain 1982'' (the World Cup soccer play that begins in Spain June 13).

Last year, there was a greater variety of foreign goods because travel was ''free'' and people returned with ''luxuries'' to sell.

In 1981 almost a million Poles traveled to Western countries. Between 80 and 90 percent came back. Many of the 150,000 who stayed on in the West did so legally with extended passports and visitors' visas; about half of the total requested asylum.

But this year such travel is out. Only a thousand people will be going to Spain for the soccer, most of them managers, coaches, and trainers.

Martial law blocked a bill that would have enshrined the right of all Poles to a passport good for five years.

The bitterest complaint of young people about martial law concerns the ban on travel to the West. Officials say travel is impossible because there is no hard currency. But the ban applies even to travel backed by hosts who guarantee costs.

The sponsors are planning to reconsider the bill at an early parliamentary session. Its passage would probably do more to defuse youth unrest than the Communist Party Central Committee meeting due shortly to discuss its problems.

The Rozyckiego Market in Prague, Warsaw's crowded old suburb on the east bank of the Vistula River, is a ''free'' market where everything from food to textiles is sold by private peasant farmers and others.

Shoes made by home craftsmen are not much more expensive than those in the state shops -- when the shops have them. But state store offerings are usually better because the plants have Western equipment.

''Free market'' prices for the season's first strawberries and fresh vegetables are much higher, even though quality is not always superior to what is in the state sector.

But ''free'' in Poland seems to have status, regardless of price. So business at Prague is good.

Even delicacies like smoked salmon at 2,500 zlotys a kilo ($13.40 a pound at the official exchange rate), fresh eel at 2,000 zlotys a kilo ($10.72 a pound), ham (a Polish pride -- 3,000 zlotys), and Hungarian salami (3,500 zlotys) were selling briskly.