There are several excellent "Precio Fijo "(fixed price) restaurants in Buenos Aires. These all you can eat buffets, also known as "Tenedor libre" (literally, free fork) restaurants, offer the best food bargain in town.

Some feel the best of the best is found at the all you can eat buffet: MAIZALES

2 locations:  Caballito and Belgrano

http://www.ggba.com.ar/maizales/entra...

Staffed with recent graduates of culinary art institutes. 

The apple crepes with burnt rum are superb!

 

Others prefer El Gourmet Porteno http://guiaoleo.com.ar/detail.php?ID=... in Puerto Madero or La Bistecca, with several locations around town including Puerto Madero . 

 For lots of well prepared food,  these are all options worthy of consideration. For those more interested in quantity than quality...try Grants...with several locations, including Recoleta.