Aside from your "contradictory" paragraph, (which i still don't understand, lal)
Think of what happened to Vancouver. Every hotel within a 100km radius was packed with tourists. These people will eat, shit, sleep, and spend their money on the local economy. The locals will obviously rip off them since they don't know exchange rates or someshit.
Brazilian people will obviously get something from this world cup. Sure, the actual cost for tickets and merchandise will go to FIFA, but the rest of the money they're spending to live there during the world cup will go straight to the economy.
If Brazilians are saying "gtfo we don't want a world cup", then tourists won't come. The world cup will happen. less than expected audience. less money for Brazil.
Simple as that.