I would think that getting paid in store credit (or other perks, etc.) is not comparable to getting free room & board. As far as basic living expenses, after room & board what's left-- Cable TV & gas?
Yes and no, compensation is compensation, just ask the IRS. Yes I'm playing devils advocate to a degree here. Let's say you come help me with my renovations just because your a nice guy we are friends and bored etc. Even though you didn't ask I give you a 6 pack of beer and order a pizza. I have compensated you whatever to cost of the pizza and beer are.
Another example for a while when I first joined I was only getting base pay at I think around 1200 a month. I lived in the barracks and ate at the chow hall, even cable and phone were included. So by my paycheck I made 1200 a month but i didn't have to pay rent, buy food or pay cable or phone so i was making more in total.