Recovering costs to help with future products is the way to go. Plus you can also develop new clients by talking with them and networking. I don't sell them too often, just whenever I come across them at thrift stores. I don't thrift as much these days so that's mainly why.

Some times I sell a one-off product I get, or sometimes I find a batch of them. For example, I found several Nerium creams at once (Day & Night, and firming body contouring formulas). When they're sealed new and not expired, things like those sell in just a few days. On the other hand, sometimes I'll buy an obscure cream and it'll take a while to sell since it's not popular. It's still valuable though to justify the effort and I keep track of the expiration date.