Momice charges a service fee of 3% per ticket sold. You can choose whether you want to pass this fee on to your guests (on top of the ticket price) or include it in the ticket price - so you as an organiser are paying for the fee.
You can choose the appropriate settings in the Ticket Module (Settings).
Please note: you change the settings on event level. In case an event has multiple entry tickets, these settings apply to all tickets.