The real figure

Can someone please tell me why venues do this? They say for example of venue tyre is 11,000 and then they don’t disclose what else you have to add to that mandatory and it’s very frustrating when you think oh I found a venue on budget and then by the time they’ve added everything up, it’s like 20 grand, and that’s before anything else and it’s very very frustrating. They should be able to disclose the whole figure all in.