Oh man, that hits home. I read this article about "dream budgets" that are just not based in reality, like putting $200 for a whole month of groceries or $50 for gas. It said a real budget starts with your actual past spending, not your best hopes. So I went back and looked at my old coffee line, which was a fantasy $40. The real number was like $120. Your brother's totally right, it's just making a list of what you wish things cost.
Yeah, and it's like that with so much stuff... not just money. People make these perfect plans for their day with no time for traffic or a slow coworker, or a diet that doesn't factor in being tired after work. It's all wish lists. What @hill.mila said about using real past numbers is the only way to see the actual shape of your life, not the one you want to have. You have to start from what is, not what should be.