I can believe it is going to cost $1 billion but they know they are going to get their money back. I am not a businessy/marketing minded person and I always wondered how they get their money from stuff like this and now I know. I watched Kids React to Cars 3 on youtube a few days ago (I love the React channel) and one of the interesting bits of trivia they gave you is that so far Disney have got $1 billion in ticket sales from the first two films (so they have easily got their money back) buuuuuuuuuuuuuuuuut...........$20 billion from merchdise. It is ridiculous.
It is going to be worth Amazon ploughing a stupid amount of money into the series because when they start releasing the companion books/encyclopaedias and whatever else they'll be raking it in. They can also make them Amazon online exclusives as well. As an example, a few years ago I bought
this for my mum and she absolutely loved it. It is a huge GoT bible, fantastic glossy thick paper, going through all the characters, the Houses and the key locations in the series (Winterfell, Kings Landing the Wall etc) with gorgeous full page scenic photos. It was well worth every penny.