IIRC, there’s no real guarantee with auction sales, so you ned to know what to look for in the car.
I did used to run an “antique” (junk) business and bought htrough auctions. The public would bid on stuff and get caught up in the moment and end paying way over the odds for stuff. A great example was a Christmas design plate, in late January which was on sale in a local department store sale for about £5 going for £15 in an auction. Had a big name like Doulton.
Also, you can’t really check the cars over during a sale, so you need to go before the sale, and check the cars over first, knowing all the petrolhead stuff like what cars have dodgy suspension and know how to check that it’s ok. The decide how much you’re prepared to pay, and stick to it. You probably can find a bargain, eg ex repmobioles which are high mileage (less attractive to the pros) but well maintained. But remember, you’re up against experts.
I use either clearance cars from dealers or autotrader, where you can leat get a bit of a drive before forking out your pennies.