The quality of the Instructors is a huge but necessary cost.
If you have 200 hrs and are learning for a CPL, you may well be taught by a guy with 300 hrs and an instructor licence who is hours building for an ATPL. Nothing wrong with that; but if you are a 200 hrs student in the RAF, you are doing low level bad weather formation and a 300 hr civvy instructor would just get you both killed.