I think it’s a supply and demand (for pilots) sort of thing. There are less pilots than there are available flights. Pilots are pretty limited regarding their available flying hours (at least in the US):

An airline transport pilot can fly up to 8 hours per 24 hour period and up to 10 hours if a second pilot is aboard. Pilots are required to rest a minimum of 16 hours postflight. Some variances to these regulations exist depending on the company’s operations specifications.

I agree about the cartel bit though, the prices for a lot of things are outrageous.