Talking about training costs shouldn't they drop substantially if you are not adding fleet group or staff?
I know it wouldn't go totally but, for example say you have a fleet solely of B737s. If you don't add any new aircraft and therefore staff surely all your staff would be trained in using them and the costs should drop big time.
Yes using the same fleet should drop costs. Using your example, if you flew solely 737s, you would only need 737 simulators. Also I understand what you say about staff, but say in DOTM, you don't hire all your pilots in 1981 then they retire at the end of the game in 2000 or whenever it is.
I believe the game represents a dynamic staff environment when staff, including pilots are always coming and going so the costs involve getting the new replacement staff (and extra hired ones for growth) up to the minimum qualifications. i.e. There will always be staff who need training up. Staff may even need extra training if they are promoted, say from HR to management.
However it can only be reduced to a certain minimum costs because of fixed costs like CAA/FAA administration and the cost of the actual licence, plus the fifty something hours in a simulator (which cost about £1000/hour to run). Which you can only get so cheap.