If you share the common conviction that cuisine quality diminishes and prices rise in direct proportion to the height at which the food is served, you have a legitimate case -- especially if your table also moves in a circle. Here's an exception. This restaurant sits atop the Hôtel Loews Le Concorde, and it turns 360 degrees in about an hour. The panorama thus revealed is truly splendid. But here's the double surprise: the food is above average and the cost entirely reasonable. You have the choice of an all-you-can-eat buffet at lunch or dinner or a la carte selections, and the buffet is as good a deal as you're likely to find. Appearances are made by monkfish, lamb, and breast of pheasant, as well as more familiar chicken and beef.