I haven't used AWS for a year, but last time I saw this it was crypto coin miners who didn't know how to use the spot market place properly. This was way back w

I haven't used AWS for a year, but last time I saw this it was crypto coin miners who didn't know how to use the spot market place properly. This was way back when Bitcoin was first spiking, and for about two weeks the price of the compute instances was ridiculous (CPU mining was still a thing). This was confirmed later by an AWS person. If you look outside the default us-east-1 region you often find prices are more stable (though not always as cheap)