Sometimes I also wonder how many more people would pre-purchase an expansion if the prices were a lot lower. I have a couple of friends that used to play a LOT of hearthstone. But they played a lot for a couple of months and then take a break for a couple of months. This made it very hard for them to come back everytime they felt like playing again. Eventually they quit, because getting back into the game was too time-consuming or simply too expensive.
Most of them told me that they were willing to pay something like 30-50 euros so they could get back into the game. So if blizzard were to put the pre-purchase bundles at 20 euros for small bundle and 40 euros for big bundle approximately, they would actually buy one or two bundles and were very willing to keep playing whenever an expansion hit.
I have bought bundles in the past. But I don't feel the game is worth it to me to spend 80 or 120 euros to pre-purchase both bundles. If the cost for 130 pack (both bundles usually) was somethin like 50-60 euros, I would pre-purchase every single expansion. And I believe a lot of people would feel this way. Lowering the cost of the game will have more people spend money on it. Earning them more money overall and getting the game an even better playerbase.
Maybe they make more money with the prices as they are. I don't know. But I do know that they would make more money off of me, if the prices were lower. Because for my own conscience, I can not spend 80 euros every 4 months (for 85 packs). And I do very much enjoy the game. So I don't feel bad at all spending money on it. Spending money on something I enjoy is a very natural thing for me to do. It's just that I don't feel I get enough out of my money to justify the amount I have to put in it.