All of the pipes I have had commissioned were from Rad Davis. I tell him what I want in terms of shape, size, weight, inside bowl width, inside bowl depth, length and bowl height. I tell him the stain I want, any stem applications, what type of stem and of course I tell him I want a perfect blast. There have been a couple of times where I went into his gallery of made pipes and told him I want number so and so.
He has never asked for a deposit because he knows that if I did not like the pipe, he could sell it just as easy in his store. I personally would be very uncomfortable if an artisan asked me for a deposit, and probably would not do business with them. I certainly would never give someone 50% up front, that is absurd.
If you are seriously considering a commissioned pipe and can afford something in the 375-400.00 range, I do not think you can do better than a pipe from Rad Davis. I own 17 of his pipes and every one is a fantastic smoking machine and I have owned pipes costing three times as much and none smoked better than my Rad's.