This is one of those questions with a two-word answer; it depends. I have been flying for over 20 years, owned a Cessna 150 for 12 years, and recently sold it and bought an RV12. I always did owner-assisted annuals and paid between $500 and $ 1,000, not including parts.
I did all the opening, closing, and removal of the interior, lubrication per the maintenance manual, breaks, bearings, plugs, tires, tubs, etc. On average, about 20 to 30 hours of work. I figured I saved on average $2,500 a year in labor and got a great education working with excellent A&P, and IA’s. I wish I logged it all.
In June, I attended Rainbow Aviation Services 15 day class and got my LSRM-A. Primarily to do my condition inspections, but also to assist others with theirs and have a little income in my retirement. I highly recommend Rainbow classes 2-day or 15-day classes.