GEMA seems to use some logic

GEMA, the german company/organisation, that gets artists their money has not established what online radio and mobile phone ring tone companies need to pay. The interesting thing is that they are establishing it on revenue.

If you have less than 25 non-interactive channels you pay 10%, above that 12% of the money you make via those channels.

For selling ringtones you pay 15% of the price that the user pays.

If you have a web site with songs you pay 25 EUR monthly for less than 10000 page impressions and another 25EUR above that. This sounds a bit much and it might be arguable what page impressions are but the ideas are going in the right direction I think.