Dude basically gave the company 100 million and they're not even offering 10% to him? Instead it's less than 1%.
I'd understand if he found the client and simply got him to auction it with the company while maintaining ownership. The auction company gets publicity for the rare item as well as whatever insane 5-20% auction fee when it does sell. He should in that scenario get the 800k simply because that's a reasonable fair amount.
However that's not the situation at all. He literally BOUGHT the item for an extremely low price bordering on 1-2% it's actual value utilizing the company funds. After he discovered it & authenticated it, then negotiated on such a ridiculously low price knowing full well it's actual worth.
He probably wouldn't make that amount of money working his entire life for this company. Imagine if he just bought it himself and started his own auction or antique business. Upsetting because it's different if the company he worked for was family run/treated him really well like picked him off the street paid for his education etc. Even just showed him basic respect for his hard work. Instead they treated him like trash & now he's only important in their eyes because he made them shit ton of money.