$19.99 on CDKeys com
I've ordered from them before and had no issues & they accept PayPal.
They're not an authorized retailer, AFAIK.
I also thought they were banned on GAF.
I'm not saying they scam you 100% of the time, but as i understand it, there's always a chance you could run in trouble for using non authorized reseller's keys, plus your money do not go to the developers (though that's also true when you buy used, i guess).