Ah, cool to see there is some interest in this :).
-Level1noob_1. Texture resolution is whatever you want since it is substance files. I believe 32x32 is the lowest, and 2048x2048 is the highest. There is some work being put in by Epic and Allegorithmic to make substances go as high as 4096.
Ah, and $75-ish USD does seem reasonable. I am Canadian and was originally thinking of prices off the top of my head in CAD.