Damn I kinda want to build little doohickeys and sell them on etsy instead of going to work every morning
1. You don't sell enough to get by.
2. You sell enough for Chinese knock-offs to come in and offer a good-enough clone product for 1/3 your raw material cost.
Being a first world tiny shop in hardware is near impossible.
Could you get plastic versions for a third the price? Absolutely. Would you? Hell nah. I could see kits of spare parts to print and build your own, maybe, but not ready made.
Of course, running a small business like this is not easy, but it's not impossible either.
Executive desk toys are a classic premium market!
Turns out a lot of people just want the thing, I can give the plans away and still make some extra on the side by making a few to sell.
I'm incredibly far away from being able to quit my job over this, but it has turned a few of my hobbies into slightly net-profitable ventures instead of money holes and the result is a well appointed shop to spend my free time playing around with new ideas.
My advice: give it a shot. There's nearly zero up front cost and if nothing else, you'll probably learn a bit.