I am about to print 1 of 2 models I uploaded but I am really confused about pricing. The two models have the same bounding box but one has thinner walls. The one with the thinner walls has a volume of 135cm3 and a density of 7.37% while the other has a volume of 290cm3 and density of 15.87%. Unfortunately, the price difference is only 15% (190 vs 219). I was hoping to get the price down proportionally. What is causing this lack of savings?