Can someone help me out - who pays for things on HF? Are they charging the model providers?

It's not too dissimilar from GitHub, but geared towards ML. They have a 9/mo pro plan for individual users for upgraded storage/usage, and an enterprise version of Hub that larger orgs can pay for. I think the enterprise has some contract minimum + 50/mo per seat. https://huggingface.co/pro

They also have inference endpoints with metered prices, and their spaces product (though i'd imagine this is a smaller portion of revenue).