Given enough money and resources, you could make a supercomputer out of anything.
This MAC supercomputer costs $520 per GFlop... ($5.2 million/10,000 GFlops).
This compares to
this AMD supercomputer that costs $100 per GFlop ($40,000/500 GFlops). I highly doubt the extra equipment required to connect a few of these clusters would make up the extra $400 per GFlop...
I don't see how this can be touted as the cheapest supercomputer (price/performance) when the $100 per GFlop barrier has already been broken. You could tout it as the cheapest supercomputer in the top 3. I don't know how much the others cost. But they sure can't advertised that it's the cheapest in the entire Top500, because the one above is in there.
Then of course there's
this one and
Blue Gene due out next year.