Music artists get a ton of money because they're A) talented, or B) marketed well...or some combination of A and B.
They're hardly different from movie and videogame companies. Spiderman 3 is crap, but people still buy it, just like people buy Britney Spears cds. Everyone earns their money...it's not your choice to decide if they should have less than they deserve.
Pirating does not cost money however... any company. Atleast not in any country where it's illegal, because the large majority of people 99% or so, who do so would never buy said products in the first place and that's why they go through the trouble of downloading said stuff. It's actually something that has statistics behind it.
The amount of money lost by pirating in places where it's illegal(well the US) is statistically incomparable from zero. I know, it doesn't make sense to you but it's true. It's one of those more complicated issues of the market but it generally has to do with who's doing the pirating, who's pirating what, and some of the other effects pirating can have that are positive for those same game,record,music industries.
I don't pirate music by the way. I just know these things because of my choice of majors. So i'm not "justifying" anything. I just know the general facts behind the matter.