Used car purchases

That's right, TerrynViv. Every car imported to Costa Rica is subject to Customs import duty at a rate determined by Customs. It doesn't matter if the car is new or used; nor does it matter who actually imports the vehicle -- new car dealers, used car dealers, or private owners. The Customs duty is embedded in the price of all vehicles and is, in effect, carried on from the original importer to the next owner every time the vehicle changes hands.

I'm not fully up to speed on this, but there is, or will be, some relief for expats who are relocating to Costa Rica, but the process is not yet fully fleshed out.