This is actually a really bad deal (unless something changed since you posted) 40$ for the 12 dry quart bag? You can get a 39 quart bag (1.5 Cu FT) for 30$. Thats some really expensive perlite.
Grabbed one of the adidings during prime sale, ended up something like 80$. Straight up Mars Hydro FCE3000 clone even down to the corny stickers. Shouldve grabbed a second.
You pretty much hit the nail on the head. Getting rid of that quantity outside of a retail location on the regular can be a PITA. Easier to grow them than it is to sell them.