Don't forget that there is a cap on the number of transactions that the blockchain can process in a given amount of time (IIRC it's like 7 transactions per second). That's what we call a scarce resource, which will eventually lead to rent-seeking. I guarantee there will be payment processors that spring up as a result of being able to guarantee priority on your transactions because they have agreements with multiple large bitcoin mining pools. I'm also willing to bet that this fee settles out close to the transfer fee for existing international money transfer services.