Most of the stuff is made on a machine now with little human involvement, so not significant labour differences (and notice how a shotgun assembled in Spain still price competes with one assembled in the US or Turkey) - the difference now is probably more "how many seconds and how tight the tolerance is set" on the CNC machine - which certainly should not triple the cost of the process. I can't imagine that the employee putting together the Rem 700 gets 2 and half times the pay he gets when putting together a 783 - or that the steel and the plastic between the two is about three times the cost.
I'm sorry but your post represents a fundamental misunderstanding of what drives the cost of a firearm up. I worked in manufacturing and have some experience of this.
CNC machines are CNC machines - this is true. On a budget rifle, you will typically see laminate or composite stocks that have been machine made, machine sanded, finished in a polymer spray and installed.
The metal parts come right off the mill, go to a particulate blasting process, are assembled and installed.
These are truly mass-produced products with minimal human touch. The finishes are the cheapest available and the tolerances between metal and stock set are left at "functional". Headspace is often a less elegant jamb nut system (ala Savage) because this saves a LOT of money in fitment.
On the "upscale" guns, the cost driver has NOTHING TO DO wit the machining processes. The cost of a trained monkey feeding bar stock into a six axis is the same for anyone and the G code has long since been paid for. It is all in fit and finish.
Go pick up a blued Wingmaster or Remington 700 BDL and glimpse what a 800 grit finish looks like. There is no trace of machine marks, just a mirror finish you can shave in. The bluing is top notch and does not rust when glanced at sideways. There was no sandblasting process to obscure lathe and mill marks. These finishes are achieved with skilled trades people who earn over $20 an hour. People who spend all day with files and various grits of emery paper making that firearm look like its price tag.
Now look at the stocks. The high-end is almost universally stocked in walnut. The walnut fitment to the metal is typically much tighter than on the lower end guns. The stocks are machine inlet to about 95%, but that last 5% is done by more skilled trades people with chisels and a practised hand. These folks also make a lot of money.
If the stock is hand checkered, like some makers offer, at least $300 of the price is hidden there. More skilled labour.
Bottom line is that mass production over many units results in economy of scale. Mass production, in most industries, aims to minimize the labour element as it drives up unit cost. People shopping in the upper tier demand and expect the incremental quality that expensive hand finishes bring to what might be their primary firearm for the next 20+ years. That is what they are paying for.