Sanctioning bodies, WBC, IBF, WBA...why do you have to pay them?

[gridiron]

If you don't pay them, you don't get their belt, and so you don't get to call yourself a world champion.

And that's why the bodies (especially WBA) are doubling their champions in several divisions. It's a lucrative market.

The WBA recently broke their own rules, upgrading Margarito to "super champ" so they could get extra sanction fees out of Yuri Nuzhnenko, making him "world champ".
I suspect a "regular" belt comes at a higher price than a "interim" belt.