Given how flimsy most of the parts I've seen from these things are I'm not sure I want one ...
I have had several tape measure prototypes made of a product which I patented and marketed.
These prototypes were all robust and fully functional and good enough to fully prove and demonstrate the working concept to business partners and customers.
3D printed models are a really useful tool in product development but also come into their own for making casting patterns direct from CAD drawings.
I don't doubt that some machines and the materials they use do leave a lot to be desired,but a properly designed 3D printer running with quality materials and operated by someone with knowledge of the limitations is a huge bonus.....OZ.