I was thinking of that, I anyways must check out Uruguay once I am down there, and was planning a day trip to Colonia so may just pay. Is the ferry a complicated thing down there?
I read on Lonely Planet that if you fly from the argentinian side of Iguazu falls to BA then you avoid paying as it is a domestic flight. As per my tentative plan I will start off in Brazil at then make my way down from Iguazu.