Hey, things have been in flux somewhat, but they should stabilize now. Sorry about the moving parts!
More details, from @michellehbn :
In February, Inference billing usage had been a fixed rate while we added pay-as-you-go support so now, usage in March on takes into account compute time x price of the hardware. We're really sorry for any confusion or scare! We have more information about Inference Providers here: https://huggingface.co/docs/inference-providers/en/index