it's just an awful thing to do really. forcing a price and not selling keys to Amazon, GMG and others just is a a bad practice that hurt gamers like me. if they want to push their GoG platform let them do good offers that compete with other stores like what Steam and Origin do all the time, not allowing other stores to sell like usual is just very anti consumer behavior.
To be clear, GMG now sells the keys. It's just that they are GOG keys. But you can apparently get a 23% off discount.