Not to put your prices down or anything, but I'm just gonna leave this here : http://www.kinguin.net/category/3113/batman-arkham-origins-deathstroke-dlc-steam-key/
I actually find it a little odd when people get all these games for under $4 and then come here and still ask $1 for them... or any money. Is $0.25 worth the hassle of transferring funds? Ah hell...maybe I'm odd. Carry on :)