Honestly "Peak ROI" in the computing space is a 2-3 year old ex-business ThinkPad. Chuck an SSD in it, new battery and some more RAM and you're in business. Will last 2 years and cost bugger all in that time and have a 33% return. Due to the progression of the technology curve slowing at the moment, it's not going to be far behind state of the art. If you bust the screen, $40. If you bust the keyboard, $30. If you destroy the whole thing, $200. Also usually comes with an integrated windows license that will quite happily take windows 10 pro.
Despite defending them I'm not going to buy another Mac when I get rid of my MBP later this year. If I had nothing else to spend cash on I'd probably buy one but I could get a new DSA815 with tracking generator or a second hand Agilent unit and another T4xx Thinkpad for the price of a new MBP which I would enjoy more. Or perhaps an FT-818
While I agree that the Thinkpads are still decent value, I think you are painting too rosy a picture of them. I'm typing this on a T450, which falls exactly into the "two to three year old" category you mention. It works, but the screen quality, touchpad usability, and battery life would probably disappoint you if you come from a MacBook. (And that's by design, not because it is worn out.)
Also, the equivalent of $200 (in Europe) will only buy you a severely run-down machine. If that's all you want to spend, expect major scratches, half the battery life, and some unpleasant surprise (bad key or touchpad or such). Also, larger companies seem to lease or depreciate computers over a three-year term in general -- so any used computer which is younger than that will likely have been retired for a reason.