I'm not sure how many of you want this game after the PC port failed and they took the PC version down, but here is the G2A.com page, the keys are under $20 each.
https://www.g2a.com/batman-arkham-knight-steam-cd-key-global.html
https://www.g2a.com/batman-arkham-knight-steam-cd-key-global.html
