Of course, of course! An adventurer like yourself would indeed have a great and noble purpose in this town! the guard says smiling.Dorn stretches out his arms with a half-apologetic, half-exasperated facial expression.
"We are on important business which may be beneficial to all who live in this land. We would be ever so grateful if you would waive the traditional fee." (Diplomacy 28)
But...as I am sure you can understand; I would get in trouble if I let you go through without paying. You don't want to make me lose my job, do you?
How about this, I will give everyone the discount rate! A fee of only twenty gold each. That is not too much for strong adventurers like yourselves, surely? the guard says.