The biggest factor is the effort of setting up the OS on my Raspberry Pi, packaging it, and shipping it. If I could prepay say... $50-100 USD for a fresh Pi, cable, pre-installed Arch on a SD card, and a small setup fee, I'd be all over it. Especially since getting a hold of more Raspberry Pi's is such a pain right now.
As others mentioned, it's unclear what the risk of this "unlimited for free!" deal falling through, but I'd be willing to take that risk at the setup price of this scale.
It's really just a matter of sudo dd bs=1m if=Image.img of=/dev/rdiskX. Once you're done, configure your unit, update and install desired packages (pacman). If you wish you can use dd again to create your own backup image to save you the hassle of re-installing packages if you mess things up!
Also ordering another Pi to replace the one I ship. :P