I was in meet-up where one of attendee asked a question to speaker on how to say no to customer when they have crazy requirements?

Speaker - There some times when you can't say no and in that situation you have to choose different path. One of my customer asked me to create the existing CRM like Google search page. It should show only one search box in front and all search should work like Google. I said sure and here is the budget for this change. After hearing the $$$ she just stop asking for!