What I commonly do for new customers is give them a written, non-itemized proposal with no time and material break outs. That I bring with me in a seperate sheet set. Then if they ask for a break out, I explain to them that if I give them a break out, it will cost them for the time it took to put it together. When they ask why, I explain that by giving you a itemized break out, I have in essence given you a tool by which you can either do the job yourself, or hand the list to some one else and say, do this cheaper and it is your job. And if the customer accepts this, pays and then hires me, I deduct this cost from the overall contract price.
So far, I have lost two jobs that way and later found out that the customer was a cheap bstrd and wouldn't pay in the end anyways.