Suppose they contract with the manufacturer to set up 10 production lines to meet initial demand, what happens when demand drops in the New a Year and 'everyon' forgets these exist? They'll have to decommission most of the lines, which also has a cost. Also if they over-supply the initial surge of demand even a little, they could be stuck with months worth of tail end sales. Then what do they do? Decommission all the lines for that time? They'll have to pay for warehousing the product as well. There are a lot of factors to consider, it's not just a matter of magicing up however many units are needed at any given time.