High demand can make a free event feel scarce enough to buy. The Holy See specifically states that tickets for General Audiences and the Holy Father's liturgical celebrations are always free, and provides the official request route through the Prefecture of the Papal Household.
The ticket should fail every price test except zero
GENERAL AUDIENCE
Official admission ticket
Wednesday is usual, not guaranteed
General Audiences are normally held on Wednesdays, except when the Pope has other commitments, in St Peter's Square or the Paul VI Hall. Check the official calendar before arranging transport around the expectation.
A service can cost money without changing the ticket
A guided walk, hotel pickup or explanation may have a legitimate price. Ask for an itemised description. The paid value must be the service around the audience, never a hidden resale price for the free official ticket.
Free access still has logistics
Bring the requested confirmation, arrive with time for security and follow the current collection or entry instructions. Scarcity, screening and waiting do not convert the ticket into a commercial product.
A donation is not admission
St Peter's Basilica provides offering boxes for voluntary donations and Mass intentions. Giving can support the church, but it is a personal act after access, not a fee required to enter the basilica or attend an audience.
Tipping begins with the service, not the sacred site
There is no tip for entering a church or receiving a free audience ticket. Paid guides and restaurants around the Vatican follow the surrounding Italian custom. Check the bill for service, then round up or add a modest voluntary amount only when it is deserved.