We've been selling pre-order shincha for about 14 years. We've always charged for pre-orders, this is the first time I've ever had anyone question it. Are we the only ones? I assume this is the norm, not sure. Our pre-order customers get first priority once the tea comes in, it's shipped the same day we get it. We also give a 10% discount (limited time only) to our newsletter and Facebook subscribers if they pre-order shincha. The reason we do this is so we know how many to order, and in return we give the discount. Can you imagine how difficult it would be to try and collect, process, obtain FDA Prior notice numbers, etc, etc, on hundreds of orders all at once? How many of those pre-orders would actually be good when it came time to charge them? We could never get them out to everyone the same day we get the tea. So yes, at least with us, if you wish to pre-order then you must pre-pay, but you at least have the ability to get a 10% discount on the tea by doing so. If this doesn't work for you, then you should probably hold out until the shincha is in, that is no problem.
I completely agree with this way of doing things, and if I were in your position I would certainly operate similarly if not identically in this regard.
I also agree wholeheartedly with victoria3 in feeling appreciation.