I plan to travel from Foz do Iguazu to Rio on around 20/8.
I'm thinking of talking a plane, but I don't know how much it will be, or if I will be able to find tickets for the same day (or the next) once I'm there, as apparently they are much cheaper if you buy them inside Brazil.
Tickets here in Brazil are much more expensive. It's about USD $ 330, one ticket from Iguaçu to Rio. You probably can buy from there an air pass (four different destinations) for USD $ 450, maybe less.
Flavio / Thespis
The company local more cheap is GOL (www.voegol.com.br) and VASP(www.vasp.com.br), but in 16 hours by bus you can down in Rio ---oh! Rio!
Two official company (Pluma and Crucero del Norte from Puerto Iguazu-Argentina).
Crucero del Norte is the better company and very cheap like 25US$(american dollar) and includ diner, drinks(and alcolic drink), breakfast, films and others!
company CRUCERO DEL NORTE has a bus to go to Rio from Iguazu
it takes 18 hs and costs 180 $Arg.
from Bs As. the same co takes 38 hs to go to Rio and it costs 290 $A