Flipper Tools is a website that will provide the actual selling price for eBay auctions that sell for "best offer".
Unfortunately it is currently down due to "abuse" - see below. Hopefully the problems will be resolved as it is very useful!
Update 7-29-20: This service is currently down to abuse. If you are running a bot, please contact us at firstname.lastname@example.org otherwise this service will be down permanently as eBay is now actively blocking due to excessive queries.
Please consider donating to FlipperTools to help me continue to support the free tools on this site.