Looks as though you have three potential customers in this thread that are serious. Round up 20 or so more and approach Conitec.

Personally I don't see how they could do the port for $50K, but if they could that would be a steal in terms of development costs (it would effectively be an entirely new engine...everything in 3DGS is heavily rooted in DirectX). I myself would be more interested in what this would mean for the Windows version of 3DGS than what it would for the potential Mac customers. Maintaining 2 seperate code bases would not make much sense so chances are good that certain limitations in the current engine might be skirted in a new build that will run (more or less) on both Windows and OSX.

If Conitec would be willing to offer up more information on what the big picture of the potential port would be, I might be willing to throw my hat (and a few dollars as well ) in behind the development.