Just for the heck of it a while ago I uploaded two test models to check out how much difference in price there was between a hollow model and a solid model. I created two 10cm dia spheres. The hollow one had a shell of approximately 2mm (can't remember exactly) and would cost $91 to print in SWF. The second was solid and would cost $786 in same material ! So if you were wondering whether or not to hollow out your model I think you just made up your mind !