There are several reasons for the discrepancy. The obvious one of course is economic slave labour but that's not the entire reason. Technology changes are probably the biggest reason.
Just like the National Semiconductor SC/MP Kit which was my first micro. The CNC equipment, if a company even had one, ran with paper tape. My first Comp. Sci. University year was with punch cards and AlgolW or the novel special terminals for APL.
Fast forward, if you can call it that to the late 90's and LinuxCNC known as EMACs along with Windows Programs like MACH2 and then MACH3 at the turn of the century started to make it possible to automate things that in the past required skilled labour.
When I started my ELS project in 2006 an encoder disk with a large enough bore for my South Bend was $75US but I had to buy 100 to get that price. Hence like MACH2/3 a 1 PPR encoder was the only solution that could keep the price including stepper driver for the Z axis at $150US. The types of modules like the Arduino didn't exist. And the price of toothed belts, pulleys and a ball bearing'd encoder was still up in the $200 range.
Fast forward to around 2010 and later and we have a number of CNC type machines. You could order a MACH3 Break Out Board that came with a tiny CD holding a pirated serial numbered copy of MACH3 to run on WIN-XP. It was no longer even close to being economical to build a foundry and cast a Gingery Lathe because the far east cast iron 7x12 or 7x14 were so incredibly cheap compared to even just a decade ago. All due to the far east using CNC to cut labour costs even further.
So now the encoders required for so many robot and other control projects. My contact at Bergerda told me that they still use Japanese encoders because they feel they are better and therefore the prices on their motors are slightly higher than their competition. There's still room for quality. And they sell a lot into the garment fabrication industry like looms etc. So there's another area that North America let slide rather than automate.
My favourite peeve back when the Alberta Heritage Trust Fund was large was that the government decided the money would be well spent on creating the Kanaskis Golf course bringing in, from out of the country, white sand to look like snow for the sand traps. I would have liked to see the money put into building VCR's from scratch.
Now before anyone jumps in and says "Look what happened to VCRs" I want to stress building a VCR from scratch means from nothing but the raw materials are imported. So an infrastructure is built up to make tiny screws, metal stamping, plastics, motors, tape heads, wire, cable etc. The change to CD ROM drives and then DVD and then BLU-RAY etc. would be easy as would an automated fabrication of Cell Phones and all the infrastructure you don't see behind the scenes for cell service.
Creating an infrastructure based on small companies instead of the giants that sell out to the biggest off-shore buyer is a mistake Canadian Companies do over and over because being a hewer of wood and carrier of water appears to have a higher profit until the wood is gone and the water polluted.
Anyway I've diverged from my robot arm discussion. Next post will be a photo of a pattern and casting.