I have seen you post repeatedly about Hesse bikes only being worth $1,000-$2,500. Perhaps that is what folks bought them for, but many people invest much more money than that into them. It doesn’t make them sound investments, but it does represent the “value” some owners place on them.
Buying an older bike, refurbishing it, and making it your own can be done very inexpensively, or, for some, completely without reservation. To purchase a new bike might always be less expensive, but you are buying a production, available-to-anyone, plastic coated bike. Lots of people shy away from this due to the newer bikes lacking character and soul. To each their own. I like older bikes that have been Besto-Modded and some new ones.
Why an M-Unit? For a custom build, it can not be beat for its simplicity, reliability, and organization. Yes, they cost $300, but they resolve many inherent design flaws in the older system, and allow those who are new to electrical/wiring the ability to do it from scratch with absolute confidence. I’ve seen many “poo-poo” them, but I’ve never seen anyone who actually installed one say anything but how great and wonderful they are. So take that for what it’s worth.