They are seeing 60k downloads of 6GB models per day, which is about 33Gbps of bandwidth (assuming no burstiness in when people visit, which is a poor assumption).

That is starting to get out of the range of what is easily available. 10Gbps circuits are commodities (I had one at my desk at my last job), but 100Gbps circuits are still pretty pricey. And, it's not necessarily trivial to get that kind of throughput on file serving out of the box; this bandwidth is something like CPU <-> video card, not disk <-> cpu, or cpu <-> network. Some tweaking is for sure going to be necessary if you are self-hosting this, and now you're tweaking network parameters and writing a custom file server instead of writing your game.

The cloud here is making something possible that should never have been possible, which is pretty cool. Being able to go from 0 infrastructure to 30Gbps of file serving without lifting a finger is somewhat impressive... but with that fast iteration times, comes the entity that did all the work wanting their cut. It seems fair to me, though perhaps not economically viable. Such is life.