There is this thing, for example: http://www.rescale.com (Although I haven't used it myself)

I'm not sure whether it qualifies as low-cost.

$4.80 per hour for 32 cores according to one configuration. Doesn't seem too bad except I don't have a feel for the market in this space. Thanks Pavel for this week. Regards

The real question is how much you're going to use it.  Providers like Rescale are a wise choice if your usage is sparse and there's no obvious way for you to group with other users.  Obviously, $4.80/hour doesn't sound like that much, till you realize that buying a 32c server and using it for a year would cost $1.25/hour.  I'm ignoring the cost of floorspace (but not purchase and power/cooling) - and from the looks of it, a lot of Rescale's price is actually licenses.

It's extremely cost-effective for a pool of users to cooperatively fund and license a set of machines.  But of course hard to do by your lonesome, and takes some effort, not to mention a certain amount of lead time...