Here is the article describing the technique.
I already saw this running on a more compatible system a while back. If you read the article, you will see that this system can outperform a Mac mini in most operations.
$200 is the right price point. I wouldn’t put any more money than that into a system since OS X will probably change hardware when it ships.
IMHO, a Mac mini is still worthwhile as a system since you get so much software, good hardware integration, competitive performance, and great industrial design.