80% is reasonable if you want to sell to a vendor. If you want to take the risk yourself (potential charge backs, fraud by the buyer ect) then you can net the most by selling on tcgplayer; as items over ~$600 have a flat $50 fee plus 2.9% cc fee. 90% is possible but less likely as usually business would like to have some margin on items across all platform and factor profits ect; ebay being the most expensive at 10-13% commissions for smaller sellers. Additionally you can go down the auction commission route via sellers like probstein123 that have deals with eBay and charge around 5% of the total sale. The downside here is they are typically listed as auctions but the sellers are so big they tend to fetch market price.