Hm. I hope this works out for them. It sounds like it might have a reasonable shot at being a steady revenue source.
Usage based pricing is straightforward and makes sense. The free limits mentioned here are high enough that I couldn't plausibly see myself as a developer hitting them at any point. "docker pull" takes a minimum of 5 minutes for me, so no way am I managing to do that 100x in the space of 360 minutes.