No, the point is that "it makes more money" can justify virtually any addition to the cash shop.
It's not what Blizzard can do to make more money, but what they should (not) do.
I'm fairly certain that lootboxes would also make them quite a profit - to combat the prominence of boosting via 3rd parties of course.
Ah yes, and that has occurred within less than two years and is so huge that it completely offsets the smaller scope of TBC.
Disregarding that TBC will most likely have a much bigger Profit estimation than Classic ever had, considering how hard Blizzard lowballed Classic initially.
Putting aside that a lot of major tech companies have contracts with their suppliers for a fixed price over a given period, so one of those contracts must have also run out during that period.
Or, perhaps none of ocurred at all / is barely a relevant factor and instead, they simply saw an opportunity to make more money
which is the far simpler explanation.
I didn't claim that, there are however also a plethora of other factors that significantly cut down on costs, such as the automized customer support and the maintenance of their server infrastructure has likely gone down over the years simply due to optimization on Blizzards end.
This arguement goes both ways.
And here we don't even acknowledge that unlike Retail, TBC pays for itself after launch due to sub, they don't need to develop actually new content for TBC yet have a sizeable audience that pays a sub that is equivalent to that of an MMO still receives newly developed content updates.