Looks like a good deal. Never used this site so I can't say how reputable it is.
https://www.g2a.com/batman-arkham-origins-steam-cd-key-global.html?reflink=batman-arkham-origins-su
https://www.g2a.com/batman-arkham-origins-steam-cd-key-global.html?reflink=batman-arkham-origins-su