A small target market, surely?
Unless I'm *new* to the software industry, I almost certainly already have test machines, quite possibly running various OS images atop VMware or similar, so I don't see how an alternative costing $500 per month could "break even" under *any* usage rate, let alone the 3 hours per day suggested here.
Also, these machines are all going to be VMware images, which means no testing of anything relating to exotic hardware or anything beyond pretty mundane graphics. That rules out pretty much everything that might break in moving from one version of Windows to another.
On the other hand, if Jeff knows how to take a problem like software testing for near-infinite permutations of platform and turn it into an embarrassingly parallel problem for one very tightly constrained platform, I'm all ears.