I think the reason is two folds. First off its a monopoly with only Nepal and China who have the right to grant permission for travel. Its a great source of revenue. There is not other way to climb everest. Second, it the price was too low every other guy would attempt to climb it. The high cost requires that people actually focus on climbing and to train at other places before coming here. People pay for exclusivity. If it was a easy task to do and cheap, everest wouldnt matter, would it?