I also have a belief that what makes an artist sell is sometimes just so random. You see these great artists putting time into their music and making it just perfect selling really well, and then the next thing you see, another artist who is more "sub-par" or maybe even only image-based selling just as well...because of what? Because they are famous, or even perhaps notoriously famous?
I agree with evolusean. If you have an artist that can reach a wider variety of people, then you will have very high sales. Let's say Ayu for example. So many people can relate to her music, her lyrics, they buy it...not only that, Ayu is also manufactured, and so she gets more sales that way as well...she's like...the whole package...
Sometimes...there will be artists that sell so high, and I just wonder...WHY is everyone buying their music? And I can respect that even though I may not like it, other people might, but some artists are just bad...I mean, what would you say if K. Fed reached platinum...that he is just as talented as say Ayu or Madonna or John Legend? Sometimes...it just seems so random to me that people buy things.