These "cheap" 3d printers provide a rough product in a very limited variety of materials. Of course by cheap I mean around £700 and then lots extra for the spools of plastic filiment so not exactly cheap. They also cant print motors or anything other than dildos so your very limited there too. As a final nail in the coffin, most people would not have a clue how to alter a 3d model.
Maybe in 5 years time there will be a very small minority of people printing sex toys at home and some sex toy companies will be manufacturing parts using industrial 3d printers, but thats it.