How to get Curse of Naxxramas

Wildly popular Hearthstone is soon to get the Curse of Naxxramas update adding great new cards and innovative boss fights to acquire them. Internet speculation,mainly from Chinese Hearthstone forums is currently leaking pinch of salt type rumours as to how much Curse of Naxxramas costs:

It's rumoured the expansion will be sold in "wings" much like how the actual Naxxramas in World of Warcraft was laid out. Apparently Hearthstone currency will be used for purchasing the upgrade with the first one being free, the next will be 500g or $9, the next will be 1,000g or $18, and so on until unlocking the Frostwyrm Lair for 2,000g and $36.

This seems ludicrously overpriced and more than likely they will be sold for 500g or $9 a piece. The way Hearthpwn interprets this unlocking, all of the expansion content will cost you 5,000g or the equivalent of $90.

Past  Blizzard expansion pricing has launched expansions for their games in the $40 range. 2,000g total for everything OR the equivalent of roughly $36 makes more sense than $90 and 5,000g.