I'm in the machine shop business myself....and I'm also a consumer of specialty products. So allow me to just add kind of a neutral comment.
I have high precision CNC lathes that are capable of turning out a piece like this in a matter of a few seconds each...and the raw material...either Delrin, UHMW, Hydex, MDS nylon, or whatever you choose is relative in price. But you have to bear in mind that a machine tool capable of rapidly making these is expensive, to own and operate.
In this case, because of the simplicity of the part, there would be a minimal programming time to get the first set made...after that, the CNC programs are done and retained for future use.... and that cost goes away....
So the average guy that wants a set of door bushings cannot just go out and buy a CNC machine to make himself a set. Yes they can be made on a conventional lathe or even on a little hobby lathe...but not in any kind of quantity that would be profitable.
Now on the other hand...if I could make a set, or several sets at a time.....for, let's say, a total manufacturing cost of $10-$20 per set
then I (myself) couldn't justify making the price 15 times what it cost to manufacture them....what I would do is turn out a number of
sets in one run that would make a reasonable profit...... when sold at a reasonable price.
Also, although I have the capability to make just about anything that can be machined, I have a make/buy philosophy...
In other words....if I can buy it at a reasonable price...I do so...because my time is valuable as well.
Just my 2¢....
I don't cut anyone's throat for profit....