I'm converting a model over for my customer. I've looked over the instructions for shapeways, but I might have missed the part on overlapping shapes. So my question: If two "watertight" shapes overlap, are they treated as solid/one object? I certainly hope so! It will save me much editing.
Yes, Shapeways will combine them. Just be aware that there is a possibility they'll interpret the model differently than you intended so its best if you use something like cloud.netfabb.com to do it yourself and check the model over first.
Yes, they will be considered for pricing as one single item. You have to be careful though: Shapeways does not perform a "boolean join" on your model. While checking the model for "thin walls", this may lead to some incorrect rejections due to two surfaces that are very close to each other. Check this thread for a full explanation: https://www.shapeways.com/forum/index.php?t=msg&&th=7 825&goto=41969#msg_41969 One thing you can do: if you can get your model saved in the STL format, then you can run it thru https://cloud.netfabb.com to do a proper boolean join against all the shells.