cost of different neck joins?

[tempo]

I've been reading some topics over on TB last few days, and the old perennial, "neck- thru v bolt-on v set neck" discussions come up. People debating pros & cons of each. What I was wondering, from a manufacturers/luthiers standpoint , is the difficulty and cost to build.
Most builders seem to charge a premium for neck through instruments, yet surely if they are all CNC machined, there can't be that much in it. Handmade guitars/basses may well be a different kettle of fish of course!
(btw I have no genuine preference, owning several of all three.)