T-Shirts are probably the first one I am aware of which got there. But strangely enough, Guitars are moving that way. It used to be to get a signature series you had to be a pretty big artist. These days, there's players from cover bands getting signature series! You look through all the lists of signature series guitars, and quite a lot of them have been released in just the last ~12 years. PCB's are going there now too - I've read on HN itself hobbyists talking about how cheap it is to get individual custom boards printed for them for projects shipped from China. Manufacturers taking production runs of less than 100, and happy to do it.
It's worth noting - production on demand doesn't provide any guarantee that the products will have good longevity. In fact, many printed-on-demand T-Shirts are pretty crap and you end up tossing them after a couple years.
One solution could be to side step the issue by getting really good at flexible just in time manufacturing. This lets you decouple the company from products. When someone needs a fridge, a fridge is made. The companies running the factories could be big build to order companies that could make a huge variety of things and the plans could be for sale by “fabless” appliance companies or open source.
This is sort of how chip and electronic parts manufacture works.
In this model making something with a really long life span is fine. You might run low on fridge orders, but that just means your factories are free to make e-bikes or server racks or heat pumps or whatever the thing with demand happens to be.