When did plastic crack become an investment? It isn't even if you're the best painter in all the world you will never get your money back on this. Furthermore what is in there those who have orks have. Paying $250 dollars for what I want (the Battlewagons) is dumb. Pay full price for the battlewagons for free stuff I'll never use and can't unload myself? No thanks.
He doesn't have to accept it, but that is also cash he isn't going to have, and he'll still be stuck with the stuff. $150 is a good "get them off my hands" price, any more he may as well ebay them while running the chance that no one picks them up.