@SupaPhly part of the reason could be that they are more responsive to FOREX fluctuations than MS or Valve. The other reason is that we are so small for Sony that they can't be bothered to match what happens on the other platforms.
If you have both consoles it allows you to price shop, i've picked up a few games this way.
The Imperium of Man takes its bloody revenge upon the expansionist tau in a war of dizzying spectacle. For the first time, the daredevil warriors of the Ultramarines Assault Company go to war en masse, fighting in the skies, in the streets, and even in the prototype testing facilities of the tau Earth caste. However, Sergeants Sicarius and Numitor must overcome their hunger for glory as the brightest stars of the Tau Empire, Commanders Farsight and Shadowsun, hunt them to the brink of disaster. Tempers run short as battle-brothers fall, ammunition runs out and the course of the war takes ever-darker twists and turns. With two warrior cultures struggling for a vital edge and the body count spiralling towards a terrible conclusion, can notions of honour and duty survive at all?