At the scale of Huggingface, that still amounts to a lot load of money. Significantly less than if you did the same in AWS, but still a lot
That said, they do have a deal with AWS to make the data available in AWS ip space. Maybe they got some cheap hosting out of that too
CDN costs are pennies compared to inference and training though, HuggingFace will just get another 100 million and be set.