hasEntryFee(entryFeeID) returns 1 if the given EntryFeeID is applied to the participant, and 0 otherwise.
hasEntryFee(1) - returns 1 or 0
You can find the EntryFeeID under Main Window > Entry Fees.
This function can be used for example as a filter in Output lists, to see which participants a particular Entry Fee has been applied to.