What keeps the transaction fees from growing forever? If only a certain amount of transactions can be processed when a coin is mined then that means that competition will only grow as bitcoin becomes more widely used. This competition will raise prices yes? Because if you don't have a high bid then you won't get included when the coin is mined. And since coin mining becomes slower and slower over time that means that less windows of opportunity exist for even greater numbers of transactions. It certainly seems like this issue will only get worse unless there's some other factor I don't know about.