If you imagine instead of going to a Restaurant for a meal you call a chef and staff to exclusively visit you, your only instruction to them is you would like to eat Italian tonight for two people. First you call three restaurants and try and get three quotes, and you tell them you want a meal served in your house for two people. When the team arrive you have decided to have a party for four people, and they then have to decide what to order, they each order four separate dishes, the chef has to leave the premise to get ingredients, and you complain that they should have everything they need since you told them it was Italian meals for 2 people, and they should have anticipated you might double the quantities required. They cook your meals serve it, wash up, this takes about four hours. Just before they leave you decide you would like dessert. They present you with a bill, you say it’s not what they estimated. Then you demand to see the cost they paid for their ingredients, and inform then you are not paying them for the time to get ingredients and they should have known what to bring, tell them you have spoken to all the other people at the table and they all think the price is too high, and also that dessert should be included in the price. You then say well leave the bill and you will think about paying it in a week or so.