I should be clear-- I'm not saying you should make up fake hours or pad your estimates to conceal a higher rate-- you should work on the basis of flat fees. If the client thinks you're not worth the money, they can choose someone else to do the work. If the project takes longer than you expected, you lose, and the client wins. I think that's different than the "they bought the time" approach you were (sort of) attributing to me.