In 2012 the Air Force Research Laboratory built a supercomputer cluster from 1760 PS3s that I think was in practical use for a while[0]. I recall reading online that the Air Force struck a special deal with Sony to buy some of the last remaining PS3s that had not been updated to no longer support Linux installation during manufacturing, but that isn't mentioned in this source.

>The Condor Cluster project began four years ago, when PlayStation consoles cost about $400 each. At the same time, comparable technology would have cost about $10,000 per unit. Overall, the PS3s for the supercomputer's core cost about $2 million. According to AFRL Director of High Power Computing Mark Barnell, that cost is about 5-10% of the cost of an equivalent system built with off-the-shelf computer parts.

>Another advantage of the PS3-based supercomputer is its energy efficiency: it consumes just 10% of the power of comparable supercomputers.

I wonder how significant the cost and energy savings were by the time the project was finished, and how long the cluster was actually used.

[0]https://phys.org/news/2010-12-air-playstation-3s-supercomput...