There's several groups on facebook that buy, sell, & trade diecast but they don't won't to pay you much for them. Are there any toy shows in your area? I have a small collection that I'm trying to sell, but only been able to sell a hand full. Good luck!
what are the groups on fb? I am on there and might be interested in joining them?
you could post some of what you have on here too, some ppl might be interested in buying them on here
Make sure to read the rules for posting first, they're a bit anal about them rules