The big booking fee scam

Booking fee. Two simple little words that make my blood boil when buying tickets for an event. What is a booking fee really paying for? Booking is a compulsory part of the process that can't be avoided and isn't a special extra service so why should you be charged an additional fee for it? Any genuine extra costs involved in the booking process are marginal so basically these fees give the event organisers a legal way to make their customers pay more than the advertised price and maximise their profits from ticket sales, which seems highly unethical to me.