I don't know your neighborhood very well, either. But here are a few restaurants in the reasonable range, although the sinking dollar is pushing everything up. If you really want to cut costs, go for lunch---the menus are often quite similar, offer fewer cost options, and are sometimes as much as 30% less than dinner. Check these out:

La Lozere, 4 rue Hautefeuille,75006
Metro:St.Michel 01 43 54 26 64

Bar du Clown, 114 rue Amelot, 75011
Metro:Les filles du Calvaire, closed 2-6PM
The food is adequate, but the decor is not
to be believed. The owner is a retired
clown; the place is tiled with clowns from
the 40's(I think) and decorated with clown
memorabilia. Right by the Cirque d'Hiver.

Astier, 44 rue Jean Paul Timbaud 75011
Metro Bastille 01 43 57 16 35 A little more
expensive 4 course prix fixe for dinner and
an astonishing cheese course. Have to re-
serve:they are always booked solid

And for the sugar/chocolate junkies like me;
Go to Angelina's on the rue Rivoli for hot chocolate and a mont blanc pastry in the afternoon and you won't need dinner.