Tim,
I can only give you mine for my C150M.
I keep a running total and calculate (using Excel) tie down, fuel, failed parts (none to date), mechanic fees, and insurance. Any parts that I get replaced that add value to the plane I forget (like the new windshield).
The cost of the plane will be recouped, so I forget it.
As you would guess, the more I fly, the lower the cost per hour (I'm down to $111.31 per hour right now).
I did all of the things you're doing now, and didn't think I could afford a plane either. I had given up, and then saw this 150M at a much lower price than I had been working with. The catalyst for me was the unavailability and condition of planes to rent, and the price of this plane. I can fly when I want, I know the condition of the plane, and if things get really bad I can sell.
It's tight, but invariably we afford what we want to afford.
