A: Hello,

The payment is "pay has you go". So you only pay for usage, i.e. 0.5 credits for each GB transferred and 0.5 credits for each GB saved for 15 days. If you only save the file for 1 day, you will only be charged for that.
QRClip is not a Dropbox alternative because you are not storing files for long-term use. The main goal of QRClip is to share self-destructing files with end-to-end encryption.

Thank you!