I'm no longer going to be doing cakes and wondering were would be the best place to sell my pans and supplies.
A lot of people announce cake tools they no longer want on E-Bay.
Craigslist is free, you could try there first
Ebay, Amazon, Craigslist, local bulletin boards, newspaper ad, or hold a garage sale
Your best bet for getting closer to cost for them is craigslist or ebay. I've purchased via both and know the selling price for many is close to the cost of new in cake stores. I think you're better off selling them in groups too, like round cake pans as a wedding cake set, square the same way, any character pans another, etc.