Is there anywhere that i can find prices on cars value? Remember Beckett used to publish monthly but now i think they only offer it online.
There is a site called diecastregistry.com
It has current prices and happenings within the diecast world. It costs like $10 bucks a year. No, I am not a member.
But remember with diecast, and anything collectible, you can appraise something at any price, ask any price, but what you get for that item can be totally different amounts.
I would check Ebay for completed listings on certain diecasts you are interested, like stated above. This will give you a ballpark range on what to ask and what to pay on a diecast.