It costs £12.99 for me even though I already have all 3 stalker games. I don't think that is cheaper. If that is cheaper I can provide it to you if you like. I won't charge for it, you can have it. All I ask is that you transfer the money to me first and then I can gift it to you on Steam.
Also, you might want to check out this website to compare the prices: http://www.steamprices.com/uk/app/41700 ... of-pripyat
It's actually cheaper in Amazon