A car restoration will make you money or break even with just about any car. Airplane at the same rate will not. It’s not welding, it’s not parts, it’s pool of buyers. You have to be a pilot to use a plane. Nothing so stringent with a car. Almost everyone has a car license. Restore a Mini, 65 Mustang, or AC Cobra there is a level of value you will get out. With these crazy times, unrestored cars are going for restoration prices. Airplanes require the same amount of work as something like a Cobra or old Ferrari. If one can’t tackle a Taylorcraft as a hobby project, it is uneconomical to restore. No one is putting $50,000 into one. If you pay a shop, they got bills and that’s how they get their money. That’s why you don’t see these little planes in shops. While stuff like certified welders is a nice feel good, it’s never been a problem really in safety. Not in the US; legacy Commonwealth which the US hasn’t been since 1776. The problem is people like the guy who lag bolted a 2x4 to the wing spar of his Bellanca Viking to cover up rot and then sold it. Unethical is always unethical. There is no certificate that can stop that.