Parts have zero to do with an hourly rate. The standard hourly rate for a car is around $150 plus an hour. Most work shops are o. Around $100 plus or minis an hour.
Lames don't set the rate the time taken or the cost of parts. It's no different to anything else. If you can't afford to maintain your aircraft to the level required sell it.
This blame the lame is just bull s$&&. The engineer has been supporting GA for ever. Time come now where it's not going to happen in the future.