This method is based on the default [GroupRegPos] field, which is calculated for each participant in a group registration.
In a Group Registration, all participants are assigned the same value for [GroupID] and are sequentially numbered starting from 1 in the [GroupRegPos] field, based on the order of entry in the registration form.
In a Single Registration, [GroupRegPos] is set to 0.
To assign a fixed entry fee to the group, apply the entry fee only to participants with [GroupRegPos]=1.
For single registrants, the entry fee is applied when [GroupRegPos]=0.

In this example groups will pay an entry fee of 30 EUR, and the fee is charged virtually only to the first member of the Group Registration.
