The exchange fees can really be thought as as a "Buy-In" fee.
There are no obligations to pay any fees once you have actually obtained your BTC.
It's the same with all currency mind-you, just go on holiday and suffer the great FX fees!
Actually, the exchange fess are mostly generated by electronically "cashing out" of the fiat casino system. They don't like people leaving and throw up all kinds of road blocks (as does any other monopoly), that is what creates the fees mostly, as overheads due to cashing out costs incurred by the exchanges is passed on.
For example, if you find a trustworthy local person to trade cash for bitcoins the overheads and thus costs incurred by the transfer can be minimal.