I can tell you WHY there doesn't appear to be much of a Sales bump in December: These are WotC's numbers, so it's sales TO stores, not sales AT stores. We generally have to stock up in late November (and maybe a bit in early December) but we can't generally get too much product in the 2nd half of December, because a lot of the distributors are closed for the holidays. Then we sell all our product during that time, and we can't get replacements until January.
Which sucks somewhat, because we wind up paying a LOT to fill our shelves in January, when we have a BIG drop-off in sales with which to pay for it. Obviously, the sales in December actually cover the task of paying for it, but it always makes December's sales-to-expenses look great, and January's look terrible.