I saw a new interview with Emilia Clarke today talking about the dragons. She said D&d did want them in every episode , not because of CGI, but they felt they could wear out their novelty.
I can buy that, tho must at admit in 4 episodes we have only seen one once very briefly.
They can say what they want, and I'm not disputing the overall truth of it, but I'll never, even for an instant, believe $$$ isn't a big part of it too. Compare this show, for instance, with something like Battlestar Galactica which had to have used tons of CGI; the difference being that nearly every shot that wasn't CGI was shot on sets at a soundstage. GoT, on the other hand, shot this season with 3 separate crews in 3 separate locations around the world. That takes a whole lotta cheddar, and an extra million dollars here and there don't go that far when you're working on that kind of scale.
Also, unless they cut it to save $$$ as well, even the fire during Blackwater will need to be altered using CGI in post-production. It's supposed to be green and cast the sky in a creepy greenish hue, accordingly. So, even something like torching a boat you're done filming aboard or having Sansa look out her bedroom window requires CGI-work during post-production.