This is true, guru. I appreciate cars and all that, but you don't get your car to appreciate in price by paying to have work done. If you could buy a car for $X, pay $Y, and sell for $Z > $X+Y, the folks doing the work for $Y would increase their price and/or do work on their own investment vehicles (literally, ha ha.)
Certainly with sweat equity, you can get good money by restoring cars, either professionally or as a hobbyist. I read some interesting stuff by people who do professional restoration - they own their garage and tools; they will buy a classic car, do some combination of restoring, rebuilding, modifying (especially to look like something else - see Eleanor clones), and improving; and sell the result. They might buy something for $5k, put in $10k parts and $10k paint, and sell it for $80k after six man-months of time put into it. A tidy sum. And a good advertisement to get client cars in the shop for contract work. Certainly the client pays more per hour than the professional can earn doing their own restoration - clients require a lot of overhead and risk.
With that said, when rich people spend money on unnecessary things, as long as they stay solvent and financially secure, I couldn't care less. Billionaire owns a $50m house and $50m yacht? Great, who gives a fuck. Some guy has a car collection? Cool. Just how someone might have a house full of impressionist paintings or commission marble statues or whatever the hell. Plenty of people get to work on building and maintaining these things, often the expense calls for new designs which may end up benefitting others, and the world sees something beautiful.
If they end up pissing away their money and end up relying on others, or complaining... then they can go fuck themselves, and I'll gladly mock them.