Update:
G2A:
$24 NZD for standard on G2A
https://www.g2a.com/batman-arkham-knight-steam-cd-key-global…
$40 NZD for premium (includes season pass) on G2A
https://www.g2a.com/batman-arkham-knight-premium-edition-ste…
Use Promo Code "Bouse" on G2A for further 3% off (http://www.twitch.tv/lagtvmaximusblack)
Note: promo code use is upto you, there maybe other peeps who have similar codes, you can try thiers. I only know of this one since i was LagTv.
DL Gamer:
http://www.dlgamer.us/download-batman_arkham_knight-pc_games…
Currently it's 15% off,
With DLG-MIARAOPE voucher to get further 45% OFF
Note: I have not used the site myself ever, so cannot comment on it reputation.