Quite simply - face value refers to the original price of the ticket, minus all fees that may have been paid to the retailer. It's called face value as historically (and still often to this day) it would be printed on the face of the ticket.

At Twickets, we allow tickets to be sold at a maximum of face value plus any per-ticket fees, meaning that buyers can breathe easy knowing they're not paying more than they should be and sellers can ensure their tickets are going to real fans who maybe missed out on the initial ticket runs.