i don't think turbosquid is a good comparison here. there is the niche market for 3d printable stls, i don't think the target audience is the same as on Turbosquid. So i would check what their top vendors do and how they sell their stuff,
"i wanna ask you how you decide the price of a .stl file of one yours sculpt? How you calculate?" similar price point for hi-res 3d content on turbosquid or for that matter a one-off client job....maybe a bit more since we're hypothetically ruminating upon 'physical goods' here