I've seen that outfit, but never ordered anything.
My math may be off, but the rolls in that link are 7' x 11", which would yield 5 bags 16" long. 10 rolls would give you 50 bags for $18 before shipping.
Totalvac.com has 100 11x16 bags for $43; more expensive, but you don't have to cut and seal before using.
The Jardenstore deal would be especially good for someone wanting to make various sized bags.