I am having the strangest issue. I have created a model and I priced it "solid"- with no extra areas left empty. I started hollowing out my model to reduce the total material it would need to use to be created- updating my model as I went to see how much the cost was reduced. Then the price started going back up even as I reduced the interior of the model further. I am using a boolean subtraction. Is there a better way to do this or a proper way the Shapeways would recommend? At present, my model hollowed out to what I would estimate as 40% less volume is coming out more expensive than when I price the original "solid" model.