Did HBO ever consider asking some fixed price per simple download? No streaming, no complicated subscription services. Just payments per files. There can't be any logical reason not to offer it, if it's so widely pirated already. They can only convince some of those who pirate not to do it, if they provide the same level of simplicity and convenience. In any case, it can't make it any worse for them, than it is now. It can probably only make it better.
I'm not sure exactly what you are trying to compare. Rather try to compare those who simply pirate the stuff as soon as it's out with anything of the above. I think if they'd offer something around $2-$3 per episode right away (without any iTunes), they could gain more from those who don't pay anything to them now.
I'm comparing the amount of money HBO would get from people who only watch Game of Thrones. If you could get it without subscribing, a lot of people would cancel HBO.
