I posted this mostly for the hardware nuts and
soldering-iron jockeys.
Besides, I doubt the pre-built ones sell for $5.
Actually he says $15 US in parts, and the board he is using is all point to
point wiring, ie no circuit board available. Software is at the read and
write absolute sector stage, ie no software.
$69 gets a fully functioning system with a track record and preloaded with
software.
If you want one, most likely you don't want the other. I do agree with the
board author, the II series is a LOT of fun to tinker on.