Certainly we know that the price of our lunch includes rent, draperies, napkins and staff salaries as well as the food itself. Still, the price of the food ought to have some relation to the quality of the food. I set out to test that last summer, ordering salads nicoises wherever I found them. And contrary to expectation, the least expensive salads were the best. A salad nicoise is expected to include crisp greens, tuna, black olives, anchovies, potatoes, hard boiled eggs, tomatoes and green beans. The most expensive, $6.50 at the Hay-Adams, had no potatoes or eggs, only greens, tomatoes, tuna, anchovies and canned green beans with tasteless black olives. It was big, but it was dull. The best of the salds were the least expensive, $3.50 at Au Pied de Cochon and La Fourchette. Unfortunately, both had canned-tasting green beans, but so did every salad I encountered that bothered with green beans at all. La Fourchette took the trouble to use dilicious salty little Mediterranean olives. Another particularly appealingsalad was at Maxime, which properly did include potatoes, sprinkled fresh parsley on top, and substituted lima beans for the green beans. They were better than canned, anyway. Such a salad is a simple dish, depending on the quality of its ingredients for its success. Thus, its appeal should directly relate to price even more than dishes that rely on culinary talent. But it seems that when you are paying for a salade nicoise you are really paying for the draperies.