My understanding is that the vast majority of them end up in products. Embedded in all kinds of systems. IoT, assembly lines, signs, lobby displays, interfacing with all kinds of dumb systems to get them an internet interface. $5 for a Pi-0/pi-0w is hard to beat on anything that ships less then many 10,000s of units.

Only a very small percentage are sent to hobbiest/makers. Much like how the GPU manufactures (or their distributors) sold directly to crypto miners.