When I used Google Matrix Airfare Search – the best search engine – a ticket on the Rio Iguazu tourist route shows at US$426 or more one way.
Brazilians pay US$77 for the same 2 hour flight.
I ended up flying both ways for the Brazilian fare. It’s quite a bit cheaper than the bus.
To do so you need buy your ticket online without admitting you live in Canada. Using a Brazilian phone number, for example. Avoid filling in the Brazilian CPF (social security number). Leave that blank, if you can.
related – Lonely Planet discussion board on this topic