Hmm less than 50 a person, everywhere I can think of is going to cut it real close to that mark, its going to be more about what you drink than what you eat.

M.F. Sushi Bar (my personal favorite)

Nan....New Thai place, its supposed to be awesome

Nam....Vietnamese place, same people that own M.F. Sushi

Blue Pointe, very good

Dish, Nice spot in the highlands

There are a couple of really good Tapis bars but honestly all their names escape me right now.

As far as just buckhead goes, you might be able to get away with the Capital Grill if you don't drink, if you have never eaten there you should definitely check it out.

Matt