There are so many variables in this game, that it is an academic exercise in many ways. One thing I have found though, that in general, people often way underestimate the true and actual costs.
Reason, as always, particularly in aviation, the truth often hurts
For instance, my Bonanza, 29k per annum, based on 90 hours flying per year. That does not include engine/avionics fund. That is an all in cost.....
People also often don't seem to factor in the cost of their time in keeping the aircraft airworthy, eg paperwork, phone calls, late nights at the airfield etc.
I was a little surprised when I looked into the ownership costs of a twinstar; that made my eyes water a little and the formula seems pretty straightforwad to me...as planes get bigger, more complex (or faster), they cost more to run and maintain, exponentially!!! (notwithstanding the increased initial purchase price).