The reprap movement was exactly that. A self replicating rapid prototyper. While it never reached true replication, it got close enough to cause an explosive growth of the community. That, in turn led to the huge number of low cost suppliers and designs we have now.

Yeah it’s called RepRap

As others have said, the RepRap concept was trying to be that. At first the idea was to 3D print as much of the machine as possible, but what it realistically achieved was you would buy metal frame rails, nuts & bolts, the hot end assembly (a glorified hot glue gun), motors, and a controller board (in many cases literally an arduino) and 3D print connectors and bracketry necessary to hold the thing together. Josef Prusa took the "Mendel" pattern Reprap and simplified it into his now ubiquitous upright plate style "Prusa i3" pattern.

I've built several 3D printers from "scratch" and at least 20 from kits. My own 3D printer has printed many of its own parts.