Arbitrage exists - the difference can't be that big because if it becomes so, then lots of people just drive used cars across half a continent to resell them.

International movement of used cars is a big business, generally from more wealthy countries (where more people buy new cars) to less wealthy ones, but also to cover gaps in the market if there's a disbalance in some sector e.g. a surplus of used vans because of some large company selling them off, or a lack of a particular model that's randomly gotten in fashion somewhere.