From my experience in retail, (I've managed a few stores) the normal deposit on any special order is what the store or shop's cost, with the deposit being non-refundable.
That way it does not cost the store or shop anything, and if the person or group decides s/he or they don't want it, the shop is not out anything.

IMHO, any request or requirement for 100% of the MSRP for a special order is a football field size red flag.