If they traded it in they most likely got way less than they could have by selling it outright. They should have just let you pay them trade in value.

Tell me about it... :-/

Your parents could have sold it to you on the spot at what the Lexus dealer allowed them on trade in. Likewise, we forum members could have bought it at that price as well. Regardless what the Lexus dealer wanted. Your parents (were) in the decision catbird seat. Even gotten the sales tax credit, IIRC how it works. Would have cost them zip. It doesn't sound like your communications are open with them. Too late now, though.

You never said how much $$$ they wanted to sell it to you for.

No kidding......something's not right here with the deal......