If you’re not interested in DIY shapeoko and x-carve are options well under $5k as well.

I second the MPCNC recommendation. Though if your goal is production and not tinkering with a CNC machine, it may not be the best fit.

For something that isn't a desktop toy, under $5k might be a bit of a stretch but it shouldn't be too hard to find a used CNC mill for well under 10k if you're willing to wait around for a deal. Of course when you factor in shipping and tools that's probably going to add a few thousand as well. Further if you don't know what you're looking at, you run the risk of buying something with a bent frame or some damage that'll cost more to repair than it's worth. I'd recommend anyone starting out without much prior experience to suck it up and go for an entry level model from a company like Tormach, it'll further add to your cost, probably pushing you beyond 30 when all's said and done, but with financing that might still be easier on the wallet than 10-15k upfront, and you'll know it works.

MPCNC and friends

Wow, TIL — homemade CNC for under $500! The same project also covers homemade 3d printers.

Are there any other projects similar to this, making normally-expensive pieces of equipment approachable for hobbyists?

PrintNC is the next step up from MPCNC. It still needs some 3D printed parts but is mostly locally-sourced steel profile and electronics bought from Alibaba: https://wiki.printnc.info/. Last time I looked the parts cost circa $1000 but that was a few years ago and I expect inflation has probably doubled that.