HBO currently gets around $8 per subscriber, typically you are paying double that to the cable company so unless the overhead is 100% I doubt they would need to charge more than $15 per subscriber. The real problem is distribution and making up for the fact that cable companies are guaranteeing a certain number of subscribers (in the millions).
The other reason is that Time Warner wont risk their other channels being unbundled from the basic tier such as TNT, TBS, CNN, Cartoon, etc. They make more on some of those channels (Ads + subscriber fee) than HBO.
The other reason is that Time Warner wont risk their other channels being unbundled from the basic tier such as TNT, TBS, CNN, Cartoon, etc. They make more on some of those channels (Ads + subscriber fee) than HBO.