[FirmwareBurner]

The cheapest mask ROM microcontrollers you can't buy from distributors but only directly from the manufacturer and in large volumes they can be a couple of cents since you buy the dies and package it yourself directly on the PCB under the classic black blob of resin you see in watches/calculators and other cheap dollar store widgets.

[klelatti]

Thanks! Do you know what you’d get for that couple of cents?

[FirmwareBurner]

Something like the EM MICROELECTRONIC EM6680 or the Seiko-Epson S1C63004 but a bit more spartan. Also parts from OKI/Lapis/ROHM semi (they do the dies for Casio watches and calculators) and I think some Chinese vendors who bought out operations form Toshiba/Sharp/NEC for similar old school parts.