What makes you think Warhammer won't be bigger? They already have 2 expansion packs planned and announced. That CGI trailer may have cost more than Rome 2's announcement? (hard to say there, could be tied) Lastly, we have no idea what other marketing campaigns they have planned.
And, again, the resources required to cover all the artists and developers necessary to get all the new mechanics of a Warhammer TW seem obvious on the face of it. It requires everything in the historic TW but even more complex.