ignore the idiots 'answers' as some people love to criticise and make no constructive comments.
Anyway, in my opinion, that amount is too high an amount for it to be considered 'scrap value' and he could not sell it as 'trade' (one of the other tricks car dealers try) as you are obviously not a car dealer.
I would suggest that you have a good case. Most importantly, don't try and go in all guns blazing.
Point out to them (very politely) that you want the problems sorting out. If they say that you bought it as a ;scrap car' ask them if it is their professional opinion that you paid a fair scrap value for it.