don't think Apple gives enough to the artists. AC/DC says Apple takes the money, pays it to the recording studio, then they don't pay the artist.
The 7 biggest iTunes holdouts.

Be careful , meaning allot of those guys don't know shiit from the drugs they use.

1 - Their recording studio , depending on their contract pays them - Not Apple so if they are not getting paid they really would be smart to take that up with their studio or at lease read their contract and really try and understand it .

2 - Some artist don't like the fact that iTunes sells singles tracks , they only want to sell whole albums <--- Real truth is Apple does sell only albums at the artist request --> maybe to much drugs again ? ? I dunno but check out iTunes and the fact is you will find singles and only albums offered . It is there right in your face , so I don't know where these guys get that idea from ?

3 - iTunes conception was really a remarkable event for online purchasing at that time hence why still the worlds largest seller

4 - 99 cent songs , 33 cents goes to the artist , 33 goes to their studio and 33 goes to Apple - depending on their studio contract as mentioned above - The larger problem which I seen was artist or their studios want Apple to sell songs for more then the 99 cents up to 1.99 per track which Apple refused to do . . This did cause some fights

Beatles

Is a whole other story , they have their own record label , which they own the label . Makes sense for them to keep it all in house . Not to mention the long legal battle over Trade Mark - Apple Records -vs- Apple Computer which went on for years after the launch of iTunes

My personal feelings on the issue is, the artists need to jump on the bandwagon on the biggest online music seller.