A lot of people will use spot instances to get cheaper computer power for non-critical calculations. So they can control demand by the price for spot instances.

A lot of people will use spot instances to get cheaper computer power for non-critical calculations. So they can control demand by the price for spot instances. Also, they'll get a lot of instances up and running before publishing the post. At the moment, p2 spot prices seem very low (~9c for p2.xlarge). Especially in the GPU space, a lot of calculations will likely not be very time-sensitive. The spot market is optimal to control demand and ensure high utilization.