If you`re coming from US, Canada or Europe it`s CHEAP.
examples: a pack of cigarettes costs 2 pesos (1 U$D = 3 pesos), a hotdog is 1-2 pesos, a meal of raviolis at a restaurant is 7-10 pesos, a styling guy`s tshirt is 20pesos, a L of cerveza is 3 at a grocery store, 6ish at a resto, hostels run from 20-30 pesos a nite..
great city. busus run 24hrs a day. the subway system is retro (try linea A which was built in 1913 and still has the old trains operaiting), the elevators in buildings are fabulous (you have to manually open two sets of doors to enter and exit, quite old)
so much to see... Cementario Recoleta is where Evita Peron and many other influencial argentines rest. Puerto Madero is the newly renovated port which the pictuesque Porte de Mujeres (sp?). Lots of ferias (markets) to see. Go to Av.Florida for shopping (clothes, shoes, souvenirs) and you`ll probly see a few people dancing tango for money. Simply stunning.
I´m answering this question with the assumption you`ve never been to BsAs. my excuses if you already knew all of the above info!