South Park Cafe offers a 3 course prixe-fixe every night for $34.
You get to choose from any of their regular menu items - and the food is amazing.
Listed as French Bistro, it has evolved far beyond the classic bistro standards - with new surprises on the daily menu every time I have gone lately ...
PS: Easy parking along South Park at night.
South Park Cafe
108 South Park, San Francisco, CA 94107
Chez Panisse in Berkeley, $50 Monday (three courses), $65 Tuesday-Thursday (four). Call well in advance for a reservation.
La Folie and Gary Danko have three courses for $70 and $49 respectively, but there are lots of places in New York where you can get similar food.
The other prix-fixe tasting-menu places charge $100 and up.
For a visitor from a cosmopolitan city with lots of high-end French / New American / fusion places, I think the most interesting restaurants in SF are mid-priced and relatively casual, for example Zuni, Incanto, and Aziza.
re: Robert Lauriston
Prix fixe and tasting menu can be two different things. There are lots of early bird prix fixe menus available. Or there are special days or times like farmerbrowns three course fried chicken prix fixe after 10 pm.
The Cafe at Chez Panisse also offers a lunch and dinner prix fixe
Haven't updated too much in the Places database yet but here are a few more options ... skip the Carnelian Room, btw