A four layer board is not “moderately complex”, it’s child’s play. IMO moderately complex is in the 10-20 layer range with controlled impedance, buried vias, etc. or a mechanical assembly with hundreds of parts.
Everything definitely has gotten significantly cheaper than when I started working in mechanical/electronic engineering 15 years ago but a moderately complex board with assembly is still hundreds or thousands per board on short (1-2 week) notice. That’s what the GP means when they say that hardware prototypes are orders of magnitude more expensive (sans NRE) and I’m pretty sure they’re talking about the much more expensive mechanical side too, which also had gotten cheaper but not overwhelmingly so.
Everything definitely has gotten significantly cheaper than when I started working in mechanical/electronic engineering 15 years ago but a moderately complex board with assembly is still hundreds or thousands per board on short (1-2 week) notice. That’s what the GP means when they say that hardware prototypes are orders of magnitude more expensive (sans NRE) and I’m pretty sure they’re talking about the much more expensive mechanical side too, which also had gotten cheaper but not overwhelmingly so.