Urgh.. I just had a horrible flashback to playing Perfect World. There were high end zones/events in that horrible game which required a cash-shop item to enter. You could trade said items, so they were sold by players for obscene amount of in-game currency, but the idea is, you pay to enter those dungeons.
The only example of that I can think of right now is Lord Commander Seru. I'm not sure how anyone could pass the dps check right now without at least some of the raid having potency levels only achievable through bonus infusers.