"He who marches out of step hears another drum." ~ Ken Kesey
No. Plain and simple don't do it. You will get many requests for this, get used to it. Rather than buying a gallon of milk I would like for the grocery store to sell me a half cupevery now and then (at the gallon price of course) and deliver it to me where ever I may need it.
Quote them for an order of 24, and then quote them the same price, minus the cost of the other 23 shirts for a single.