I am glad you brought this up.

You forgot the free international shipping est. 66 bucks

The hours of troubleshooting and figuring out and the assembly of it. Not everyone likes soldering.

The people on this forum are an intelligent and savvy lot. I would reckon the only people who would buy this are people that do not want to go through the hassle of building and programming one.

Here's an excellent walk through of the project on adafruit. For those that are inclined, use it to build your own.

http://learn.adafruit.com/piminer-raspberry-pi-bitcoin-miner/initial-setup-and-assembly

There's also a sticky on the Pi section to show other Pi related walk throughs.