> Lets say that I prototype something on dev board like something from Raspberry Pi, or ones from STM. Worth noting that your typical STM32 MCU is quite differ

> Lets say that I prototype something on dev board like something from Raspberry Pi, or ones from STM. Worth noting that your typical STM32 MCU is quite different class of device compared to the Broadcom SoC on a RPi. From a architectural point of view, the big difference is that MCUs typically have both flash and ram integrated in the package, while SoC requires external ram and flash. Designing PCB for high-speed DDR memory is not trivial. Modern SoCs come in high-density BGA packages usually sporting close to thousand pins (or more!), while MCUs usually come in more easy to work with packages with order of magnitude less pins. Specifically the Broadcom chip in current RPis is custom made and not generally available.