One of the things that seems to always cause me a headache is that I never quite know whether on a specific bike I made or lost money, nor what bike a specific part may have come from. For very common stuff (seat latches for example) the source bike doesn't really matter since a part is a part, but for things like wiring harnesses, etc where the year and S vs N matters, this is really necessary.
The other thing this can let me do is track what bikes are "paid off" and on which I've spent too much. Obviously an essential component of business sustainability. If this project doesn't at least pay for itself, there's no point of doing it, as well as maybe I'm paying too much or charging too little for certain parts. If I keep pumping money into this project, it's going to fail, and people will be back to scavenging ebay or hoping the new guy on fb who claims he's parting a bike is real.
Adding parts tracking to the vin will also let me keep track of what parts have been on the shelves forever and not selling, allowing me to make "fish or cut bait" kinds of decisions.
My current plan is to create labels with barcodes for each major component of a bike and track that in the inventory system. This requires a barcode scanner, a few extra minutes per bike, and a whole lot of printed labels, however, it seems like it would definitely help improve my understanding of what's working and what isn't, as well as saving me from "omg what year is this from"
We'll see how well this goes once I implement it :)