I wouldn't have said dishonest. The only access the baseband running on the SIM800 has to the main processor (Pi) is via the Pi's UART. It's completely differ

I wouldn't have said dishonest. The only access the baseband running on the SIM800 has to the main processor (Pi) is via the Pi's UART. It's completely different from the "read and write directly to shared memory" access the baseband that your average Android potentially has. If you encrypt your SMS on the Pi and send it, ths SIM800 has no access to the keys for decryption, for example. I'm guessing you're talking about his price calculation for the $27, right? A bit further on he does say: >In total, it should be 50$ or slightly more. >Also, price falls quickly if you're assembling one or two more phones for your friend, too - eBay sellers can make discounts when you buy more than XX$ or "make an offer", and PCBs are cheaper (you won't get less than 3 pcs of PCBs in any of usual board houses, so you have to pay extra even if you need only one board - you'll still get two more) I don't think that's too far off and may be a bit pessimistic. The only component you can't bulk buy easily and cheaply is the Pi Zero as it's STILL one per customer. ABut none of the parts are expensive in single units either, except relatively speaking the PCBs. Which are non-essential because you could literally breadboard it. If you're interested, he did an AMA on Reddit earlier.