The cars are generally bought at auction. That means car dealers took them in trade and didn’t want to sell them because they were too bad/too big a risk to their reputation.
The cars were bought cheap and “repaired” enough to get them running, and then they DETAIL the hell out of them.
Bottom line is, they sell a car they own for 2-3000 for 7k+ and get their cost back so quick they’re making profit almost from day one, and whether you pay high interest forever to them or they repossess it and resell it to someone else for more profit, they don’t care.