I was interested in this, from the agents:
"“All, or the vast majority, of the sales income from the ticket goes to the producer, hence the need to charge for ticketing operations separately. However, booking fees only apply to customers who buy on the phone or online.”
By that logic they're charging more to people who actually make it cheaper for them to sell tickets...
Because they're being greedy, this technique will - in due course - be eliminated, as have many such practices in the past. Meanwhile, they'll continue to rake it in from the punters.