I think I first saw one at a makerspace. Then someone who was making them locally did a talk at the tech meetup I used to go to. It was pretty DIY back then. Looking at this list](https://all3dp.com/1/best-3d-printer-reviews-top-3d-printers-home-3-d-printer-3d/) they start pretty cheap and that includes ones which solidify liquid plastic. At work they have industrial ones that can build with metal. It must make prototyping so much easier.