About how much money would a WWF Championship foam belt made bought and played with from 1988 be worth?

I'm not sure, but if you want to sell it, put it on ebay.com and find out. Depends on the condition it is in, how many are still floating around out there and what kind of demand there might be for such an item. Having the original packaging would probably increase the value a bit. If it was still in its original package and unused it would be worth more. eBay might be your best bet as the previous poster suggested. Or maybe a toy/collectible/sports memorabilia convention?