Earlier quoted context omitted.
The fastest way to learn how to make machinable parts is to machine them yourself :). DFM is often a hard-earned skill. Unfortunately maker-spaces (the only kinds of places where you could get cheap access to good 3+ axis CNC mills) seem to have gone out of fashion. CNC mills in general cost about 5 digits just for the machine, and usually that again for the tooling. I think the closest one can get to learning some D…
You can get into cnc the diy route for between ~$2k and ~$8k depending on the amount of rigidity you want. There are conversation kits available for common import mills to make the process relatively easy but the control and wiring isn't for the faint of heart. I built one out of a PM-833TV and it's taken years to get working well, and I probably should have just bought a used HAAS at this point, but if you build it…
* https://wiki.printnc.info/en/home
* https://github.com/threedesigns/printNC
* Discord invite: https://discord.gg/RxzPna6 It's "kind of high end" as it uses steel beams (not aluminium) for rigidity, so it's capable of driving some really powerful gear... fairly cheaply. :)
The US$2k you mention above would indeed be the practical lower bound.