Puerh market in the west is very small indeed, but in China, this is well over 1.7 mil. box per year now (30 kg per box). They trade tea in boxes like stocks. It would be very difficult to corner any Dayi new productions, older or rarer top quality cakes are another matter.
There're sites give you current whole sale price. eg.
For older stuff, e.g. 88-qing, red, blue marks, there are auction site you can ckeck the price. Old maxim stated that no one would run a lost making business. Tea vendor normally would not sell a cake below its trade in price.
IMO, I don't think western pu traders operate like a cartel. If they do, we can always source our stuff on TB or buy directly from the far east.
Here I'm talking about average market price, and I don't think I can define fair price, not even trying to.