A simple 3-D vehicle mesh (without skins) seems to command about $50-$100 from various websites - I had a look a couple of years back for general interest. Most such meshes on offer were of course, M1, T80 and Shermans etc - nobody is going to have a BTR-Tz or a J-22 Orao available as a 'stock' item!. So my bet is any 'custom' jobs like that would be more expensive as 'to-order' items.
So - if we bought in sufficient third-party meshes to fit every unique unit we model, that could be maybe $3 million plus. It's a few man-years of effort to make them either oneself, or by hiring some artists for $$$. I'll leave the number of actual game units required to be sold simply to
break even for the art assets (let alone distribution & manufacturing or even game engine development) of such an enterprise to the gentle reader to guess at.
And we allow games to have a few hundred different vehicles active at one time - load more than a few 3D meshes into a 3D game engine and you will cause the machine to choke, or load one with a few too many polygons, ditto. (Try the Sims with too many people on a lot, or adding a custom 3rd party hair style with a few thousand polys in it!
)
Guess why most modern '3D' type wargames have a few
tens of different (and common - no SturmTigers!) unit types modelled and/or split things into several sub-theatres with a relatively few units in each game sub-package (France 40, Western Front, Eastern Front, Desert, Italy etc, etc), and have maps that are postage stamp sized (2km by 2km maybe), and allow you maybe 30-40 active units a side?.
Cheers
Andy