From what I recall the app's are in the $7-15 dollar range with mains going for ~$20-29 and desserts at $6-8. FID has had set dinners in the past but they're usually for special themed events (asparagus evening, Beaujolais Nouveau, seasonal meals). That said, lunch is a set price topping out at ~$16 for your app and main.
NSDave's description of the prices is correct, at least the last time I ate there, which is a few years back.
What isn't reflected on the website, or in the prices, is the fact the thet 3-4 aps and 3-4 mains are utterly amazing!!!!!
Also, when I used to eat there a fair bit, there always seemed to be a good varity. For instance, the entrees would consist of one beef dish, one seafood, one chicken, one veggie.
Fid is the type of place that is good enough to trust the chef to feed you good food; a big selection is not required. Better to have 4 good choices than 20 bad choices.