Ii would be great if Merch increased prices across the board for Merch products, when there is greater demand than can be met. This would benefit the creators and Merch, with greater profit. It is a tried, tested and very successful method by other P.O.D.
The easiest way would probably be a percentage increase, which could be adjusted as situation was monitored, throughout the day. So, maybe +20%, which means a shirt selling for $19.99 would become $23.99. Royalties would adjust inline with price increase!
At peak Christmas period, it is quite possible that the increase could be around +100%. It may be that the major brand sellers wouldn't wish to participate, so their accounts could be excluded.
However, there is concern that the major brands take priority over the small sellers, which I guess we just have to live with :-)