Years ago a big name in collectible SAKs once told me off for "allowing" members to modify their knives. I thought it was amusing that he thought I had that level of control over members
They want to talk about what they'd like to have, what can work, what materials they can pick and why. They want to be heard and see the results in a tools built for them exactly as they asked.
I'll tell you where the value is based on what Ive learned over the years. I started off thinking it was in having x materials with y tools etc... figure out what is popular and make those, have some ready to go... NOPEEvery time I built in advance I never moved them along.What Ive come to understand about the customs I provide, is the value is all in the customer getting to choose exactly what they want and to get that, by talking to someone about it. They want to talk about what they'd like to have, what can work, what materials they can pick and why. They want to be heard and see the results in a tools built for them exactly as they asked. So while I work out the cost based on parts/labor the value in a custom SAK is getting exactly what you want.
As to why I mod - mostly because I like making stuff. Not interested in 'pimping' knives with fancy materials or filework, but I do like being able to create exactly what I want which is generally very functional. Other than the cost of the parts, I don't think that any of the mods I carry and use have any added monetary value, but the increased function is worth it.