What's more interesting is that he got HBO to release their content in a DRM-free format. (HBO is the network that previously wouldn't let you buy their online video service unless you already had cable and an HBO subscription, rather defeating the purpose of buying the content online.)
Plenty of HBO content is sold a la carte online. But HBO itself is cross-subsidized from cable subscriptions. Their online service is not intended to replace their TV channel, but just augment it.
Also worth mentioning that they don't "let you buy" their content: it's just all free. All of it.
I know it sucks that you can't subscribe to HBO Go without being a cable customer. But for existing HBO users, it's a very, very well done service. The iPad app is gorgeous and well engineered. It has basically every epoisode of every season of every HBO series, all HBO original movies, and as far as I can tell nearly every HBO original documentary, comedy special, etc. And of course all of the movies HBO is currently running in their rotation.
HBO on Cable runs about $13 a month. I'm sure they could sell subscriptions just to Go for $20-25. But HBO wants to be a Cable service, not an Internet service. Nothing wrong with that. They're not luddites trying to avoid technology: they're using it very effectively. They're just using it in the way that suits their business model and philosophy.
HBO on Cable costs $13 plus whatever your basic cable fees, which after "introductory rates" often means $80/mo or more. Granted, you get more than just HBO then, but in the case that you just want HBO and nothing else there is no sanely priced option.
This is what fighting piracy looks like.