Anybody previously sold a domain? I have a few good ones which are becoming too expensive to renew, where to sell it?

I actually did not want to sell it here, as this is not service for that.... but ok, here is few domains... for instance:
fbify.com (possible for some Facebook app or tool)
endprices.com (great service for gathering discounts or similar)
alertbooking.com (booking.com service or similar)
total of 50+ similiar