This is actually the first time I hear about things like that. Any reference?
Reporting about the issue also often stresses that in order to join or the cp communities you first need to provide material yourself. That makes it difficult for law enforcement, and it grows the community's content. So even if you think most cp is not 'bought', that's another concrete way how distribution encourages more production.
http://grugq.github.io/blog/2013/12/01/yardbirds-effective-u...
Here is another case of literal pay-per-view on the deep web:
Good thing it does not justify banning Tor:
> The reason the majority of the group was able to avoid capture was in a small way due to the technology they were using (Tor), but primarily it was adherence to the security rules of the group.