Every gacha front publishes the expected value of a pack. Not one of them publishes its own fee.

We checked four yesterday. The EV shown was identical to the source's on 79 of 79 machines - so whatever the front takes, it comes out of your side of that number, silently.

The EV is easy to show. The fee is the part that tells you where you are pulling.

When you last bought a pack somewhere, did you know what the front took?