Very good question, I was about to ask it by myself. I always wondered if there was a really good reason for spending a lot of money in a totally white quilting fabric (since here in Spain the prices of patchwork fabrics are very very high).
Last month, I was in a warehouse looking for a special deco material and suddenly I saw a pile of very good quality (pure cotton) white fabric for bed sheets. The size was enormous and they sold it by weight, so it was very cheap! Some of them had a little (unnoticeable) blemish, but I'm going to cut it anyway for using as backgrounds, so I think I did a master purchase
I have not had any problem with them and I really like the look and the feel so, after reading your opinions, I think I will never go back. Now I keep my money for prints!