[zooFox]

I have no idea about serial adapters, nor I need one. However, the surprising part is that it's only $20. Are they that cheap to make? The R part of R&D must be a lot more, but I assume that's work by an enthusiast rather than a business, hence the price.

[ZiiS]

Yes wholistically this is probably only looking to cover costs. The low volume maunfacturing may be half that but you end up with so many other costs. Still many many orders of magnitude simpler then the cheeper PI it plugs in to, which saves enough with scale to be viable.

[rasz]

0.09 74AVCH1T45 x2

0.2 RS2227 multiplexers x2

0.5 FUSB302BMPX

0.2 1050170001 MOLEX usb B

0.4 USB 3.1 Female Type-C, Molex would cost $1

0.008 mosfet

0.0004 capacitor x6

0.0002 resistors x8

0.02 header

~2 assembly, half of that goes to 40 pin header for the pico!

~$1 pcb

all in all ~$6 per unit