Nitrogen is really overrated:
Composition of Air
What you're actually paying for is the removal of 22% of the stuff you get FOR FREE in AIR. And most nitrogen I've worked with is normally only guaranteed to maybe 98%, and I'll bet it's a lot less for tire use. The GT-R has nitrogen for fear of heated tires oxidizing in racing. Unless you really race and heat your tires, you don't need nitrogen. And guess what, you get 78% of the stuff in your tires anyway!
As has been mentioned, dry air is probably better for your tires/worth the money more than anything else. But I understand it's hard to take a step back once you try the bells and whistles
