It's much more a question of time than it is a question of money. Whether you want it or not, there's only so many people that can work on character models together. Integrity in sizes, styles, demeanor is just too important to have too many different artists working on separate models. It also means that it's very hard to hire new artists when trying to keep that level of integrity.

Which means that only a handful of people would have to redesign the models, the animations, the item and spell interactions, the special effects, every armor model will need tweaking, some small, some major. What sounds like a minor polygon upgrade basically amounts to making whole new models from scratch, for the most used models in the game. As is often mentioned, it's akin to creating a new boss model. Probably even more work.

There's no question that Blizzard has the money to get new models. It's just too expensive in terms of manpower and time The people that could do those models are already working on much more exciting things, like new zones, weapons, armors, enemies and bosses. Which appeal to me and a lot others much more than a facelift.

It's not money, it's time. Even the bear and cat models, they finally had their upgrade because they have very few animations and item interaction, and because Call of the Crusade was a relatively small patch, content-wise, leaving the artists with enough time to work on them.