I want to sell 5 x 1070 TI. But I am worried if I sell them on ebay I might get scammed by a buyer. I'd sell them individually and spaced apart a couple hours to make sure I don't get the same buyer. What are the chances I could lose a lot of money? If I video myself showing the card put in box at the UPS store and handed over to clerk, should that be enough evidence to show ebay to prove I mailed what I promised? I have 100% feedback over the past few years. HOw much does ebay do to protect the sellers? Do they insure against this? They make enough commisions on the sales it seems like they should protect the sellers as well no?
If you want to avoid online scammers, sell them locally for cash via Craigslist or something of the sort, meeting only at public places. Seller protection is relatively easy here. (Buyer protection, not so much, since most buyers don't lug around a test system to confirm the cards are working.)
Chances are however, that eBay is fine, if you've been a long-term seller with good feedback. Requesting signature confirmation, sending the buyer a tracking number, and recording a video of yourself putting the card in the box before it's taken by the carrier is probably sufficient for most realistic cases. (Note that your video doesn't verify the card is in working condition, so there's a small chance someone could claim it's defective and send back a different, broken, unit, so ensure that you have proof of the serial number...)
Mining hardware scammers are very creative, so there's not really any guarantees, but I think there are still steps to make transactions reasonably safe over eBay.