Gym Class Heroes - Downloads

I have looked on websites such as Amazon, play.com and Itunes looking for gym class heroes music and found that all of their albums and individual songs are available on both of these websites with prices varying from 69p a track on amazon, 70p a track on play.com and the highest prices from itunes which was 99p a track. I then looked at the cost of their albums on these sites and found despite them all offering all of their albums their latest album "the Quilt" was available from £4.98 on amazon to £9.95 on play and £7.99 on itunes which was confusing when I compared this to Their first album "the papercut chronicles" which was being sold for £7.99 on both amazon and Itunes and £9.95 on play.com