Added1
When you pay from your wallet, the upload queue says how much storage the batch actually buys — your files times about 4.6, plus the fixed 63 MiB every batch carries.
The storage network charges a fixed part for every blob, and one batch is one blob, so one small file alone costs almost the same as hundreds together. The number stands where the decision is still open, before you press the button. On credits nothing changes: you pay for the encrypted bytes only and the fixed part is carried by the pool.
Changed1
On the account screen the inquiry card is now titled "Ask a question", with "Ask us anything" underneath.