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 flippertools@gmail.com 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