I use BJs but they do and it's way cheaper. It's been awhile since I purchased so I don't have any idea what the size/price is. I just took the bags out that it came in and threw it in my pantry.
I get the big box at BJs - it's either $5 or $6 and has two roughly gallon sized resealable pouches - I've tossed the box so I don't remember how many ounces it was.
if you've got any asian or ethnic stores near you, it's a lot cheaper. even trader joe's is cheaper than the normal grocery. i haven't seen any in bulk, but the largest packages aren't that expensive and usually resealable, ziploc style.