Aircraft running costs

How do they actually calculate aircraft running costs?

E.g. Gripen’s cost might assume 1 tech and 3-4 conscripts but what about a force that does not employ conscripts?

Does it take into account differing pay grades in different airforces?

What about different fuel and other costs? Delivering a spare from France to a French base is a lot cheaper than delivering a spare from France to say an Indian base.

South African Air Force probably pays more for fuel than Royal Saudi Air Force.

Or costs of doing things differently – e.g. number of techs per aircraft, different procedures or even different missions (a high altitude interceptor used for air policing costs less to operate than a multirole jet used for every role under the sun).

And what about environmental issues – a jet based in Alaska requires different conditions (thus costs) to one based in Califonrnia.

Then there’s different tax regimes.

What about fixed costs such as running of airbases or building of hangars etc?

In the end is it ever an apples v apples comparison?