So in this middle ground of tools between "the tool as art (often seen with custom knives)" and "crappily stamped out by the millions in a Chicom factory", what do you get?
Quite a bit.
The price of a custom tool is higher than that of a mass-produced tool (usually, not always). It's not something you would want to treat as disposable. In exchange for that, however, you should be getting a tool that will fit your hand comfortably, is weighted and balanced beautifully, does the job it was made for quite satisfactorily, and is aesthetically pleasing.
Let's take for example a drawknife. In the days of table saws and bandsaws, not many folks use drawknives any more. However, there are still plenty of areas of fine and general woodworking where no other tool really does the job. The only places I know of to get a drawknife by just walking in off the street in San Antonio, TX are Northern Tools and Woodcraft. Northern Tool's offering is poor at best, with a very rough cutting edge and somewhat less-than-comfortable handle angles. I think it is sold for stripping bark off of lumber, and it may do well at that. For general woodworking like I use a drawknife for, it would take a fair amount of work just to get it to the point where it would cut wood well, and it would still be rather awkward to use. The offerings at Woodcraft go in the opposite direction. They are small specialty tools made to flex. Not all that helpful when you're trying to make an ax handle or a table leg and need to hog wood off.
On the other hand, I have a drawknife that I made as a sample tool for a class I teach. It's a bit rough-looking, but I have used it quite a bit since making it and have been very happy with it. It's forged from a car coil spring, filed entirely by hand with no power tools, and hardened in veggie oil. It will cut off large swathes of wood if I need it to, or shave off tiny feathery curls, all dependent on the way I use it.
The handles are integral socket handles. I've never seen that done on a drawknife; I did that simply to show what could be done on a project like this.
The wooden portions of the handles are made from an old forging hammer handle that had been shortened time and again until it could no longer be used as a hammer handle. The first two Turk's head knots I ever tied help clean up the transition from metal to wood.
So, not the prettiest example of a drawknife, but it: a.)is comfortable to use. b.) is visually interesting. c.)DOES THE JOB BETTER THAN WHAT I COULD EASILY BUY.
A custom-made tool should fit those criteria. Of those three, doing the job better than a commercially made product is the most import, in my opinion. A craftsman who is dedicated to producing a quality tool is constantly holding, turning, smoothing, hefting, etc. He feels how the tool is growing as he makes it and adjusts as needed. It takes time, and time is money, but the end result is a tool that should serve you until you are dead if you treat it well.
As the number of people who use hand tools on a regular basis decreases, the number of people who have the experience of what the difference is between usng a mediocre or poor tool versus a quality tool decreases, and the fewer quality tools become available for sale in non-specialty stores. It becomes harder for those who continue to work with their hands to find anything that will do the job, not only well, but even adequately.
This is true not only for tools that have been relegated to "specialty" status, such as my drawknife example above. Ever look at the axes available in Home Depot? Laughable. I've seen a couple of different people buy True Temper (which at least used to produce good tools) hatchets that had an edge almost an eighth of an inch thick. It took me a while to get decent edges on them. Look back at my student Brian who made an ax for his first project; it cost him some money, but he ended up with a tool that will outperform anything he can buy at a store and will last a lifetime.
Many people think of investments as something that will return money over time. I tend to think of investments as something that will be a pleasure to use and will last my lifetime.