I guess it depends on your definition of small.
It also depends on lots of other things. Mainly how many parts you can scrounge without purchasing new.
How far into the electronics build you want to do yourself.
As far as building a 4' X 4' cutting area table & purchasing new materials complete with a digital THC you are probably getting into the $4000.00 - $5000.00 range. (This is just a guess)
There are examples of working builds on here that have been done for much less. Most seem to have had lots of the materials laying around, scrap, leftovers from other jobs, or good scrounging sources. Also they seem to have prior knowledge of how a stepper or servo system works.
If you have time to dedicate to the project & the tools and ability to do the mechanical part of the build you can save a good bit of money.