If it's similar to cloudflare, then it should be usage based. That is you only pay for what is active. (ie: if you are running a task that is waiting on network for 1 hour, you don't pay for cpu but your app is loaded and you are paying for memory). So if your app is dormant (not using cpu or memory), you only pay for the storage you are using.

yeah reading further into the docs it looks like that’s the model. storage is pretty cheap, $.00068/gb-hr, so a 100GB disk runs you about 1.6 cents per day.