I went ahead and bought the box. I got it delivered for $208.99. It looks like the price is going up to $225 according to their website. I lined it myself with some scrap plywood I have leftover from making hurricane shutters.
Cabelas has the same box for $329.99
plus another $49.99 for the casters plus more for shipping.
I have a lot more powder on hand than most folks on this forum. Even though it seems like overkill I feel better about knowing it is stored properly with no issues if the BATF or local officials want to do an inspection.