When it comes to asking content providers to pay for better QoS, what must be remembered is that these costs will ultimately have to be passed onto the consumer. Content providers that charge a fee will have the raise their prices, those with advertising will have to adapt their promotional content, or the overall quality of the content provided will have to lessen.
So why is it then that so few ISPs are openly talking about directly charging the consumer for providing a higher QoS for their desired content providers?
Technically, it is more challenging to accommodate such a scheme, but it is entirely possible. It would maintain proper market competition between all content providers, since an ISP can adjust their QoS criteria according to their subscribers' demands. It would also allow a more consumer-orientated approach to broadband marketing (different demographics can have their own tailored QoS scheme offered to them), and bring broadband pricing schemes in line with those used for subscription television (as much I personally dislike channel 'packages', I can see why they are used).
Sadly, however, I think this all comes down to an age old problem. Ultimately the major content producers have the most money between them, and it is initially easier to try and bully them into paying, than it would be to convince your customer base that they want to pay more.