Gas is common enough and such a hot button issue that mass fraud like that would be easily noticed on credit card statements and in the tank. It's easy to test, confirm and verify, and can be done by just about anyone. Pull up to the station, fill up your gas canister, and check the price, volume etc.

The places where this fraud is most likely to exist are niche markets and places where it's hard to verify. Walled gardens of software or hardware with few outputs to measure.