>having the parts being built to subpar-precision using a FDM printer in a Czech 3d printer cluster didn't seem super exciting in itself...
None of the parts need to have tighter tolerances or higher precision for the Prusa printers to work well.
The fact of the matter is, print quality on basically any FDM printer out there can be dialed in and be really damn close. Even on the cheaper ones. The differences are more on print speed, bed leveling, crash/out of filament/etc. detection, recovery after power loss, etc. And none of those are affected by whether or not the plastic was injection molded or 3D printed.
In exchange, they gain a lot of dogfooding on their designs, including through physical and software upgrades, etc. They get to do a lot of testing on how well things like their powder coated sheets hold up to extended workhorse levels of printing.
And yes, some of it is a bit of marketing - Our printers are so good, we print them on themselves! - and the adhering to the whole RepRap movement, but there are a lot of benefits that they clearly believe outweigh the downsides.
