Almost every budget blowup at an event comes from one confusion: treating the booking fee as the total cost. A promoter hears a number, approves it, and then gets hit with flights, a hotel, a backline rental, a sound company, and a hospitality rider they did not budget for, and suddenly a clean booking is a fight over who owes what. The fee was never the whole cost. It was the price of the performance, and the performance is only one line on a real event budget.
The confusion is understandable because the fee is the number everyone quotes and the extras are the numbers nobody volunteers up front. An artist or agent names the fee because that is what they earn. The travel, the gear, the engineer, and the sandwiches on the rider are costs of making the show happen, and if you do not ask what is included, you will find out the expensive way, after you have already committed and lost your leverage to negotiate.

