Yep! Very simple and absurdly cheap to make and program. There are ton of display controllers that have more than enough capability to handle to do this all without needing a separate uC, even.
I think what you're really paying for is the software on the host computer side, and how many companies they've gotten to interface with them.
I'd be willing to bet that streamdeck makes a lot of money off sale of metrics they collect - what programs are running, what games people are playing, what they're streaming, and probably more.
