actually, I went back, and now I am more confused.
I uploaded my original file, and WSF came out less than the sandstone.
I was trying to figure out what it could be other than the handling fee, as the model is quite large (11 inches x 8.5 x 3.75 at the widest parts)
then I mocked up something similar in primitives, to scale with the original, and compared materials in this model (sandstone and WSF)
this time sandstone prices came out where I would expect them in comparison to WSF from the price chart. (about 40% less)
what do you think this could be?