At one point I decided to get all the cars that I didn't already have and used the auction house to get what was left. While i got most in under a week, there were still two cars that took a couple more weeks to find available even at 20 mil when checking twice a day.

Holy hell the interface is so terrible, and probably contributes to even more bots than if it was fairly straightforward to use. Car names aren't consistent with the list of cars, there was no 'cars not owned' filter, and the nine buttons to place a bid plus the delay every time anything happened including being outbid made trying to get a deal nearly impossible.