I'm thinking of small prototypes or production runs of one or two pieces - had a situation last year when we needed to interface between a TCP connection on one

I'm thinking of small prototypes or production runs of one or two pieces - had a situation last year when we needed to interface between a TCP connection on one side and a 12V trigger signal on the other - just a microcontroller with an optocoupler connected on one pin and an ethernet controller on the other side. We ended up spending quite a bit, between lockdowns, the minimum order, and our (my!) own messing up the circuit. Ended up just barely making it in time. If we'd had this thing, we could have rapidly prototyped this board, discovered the mistake and made appropriate changes within a couple of days, instead of having to take more than a month...