This also doesn't answer the question, but I think it is pertinent and I would be interested in feedback.
Many years ago (in Western Canada), I looked at the costs of ownership versus renting for typical, light, fixed gear singles. Regardless of the type (Cessna/Piper), the magic annual flying-hours number came out at about 400.
Below 400 hours, the fixed costs per hour predominated over the variable costs (fuel, overhaul fund, etc.) and it was cheaper to rent. Above 400 hours, ownership was the cheaper option.