You get so much more for your money. I compared the price/quantity to that of a large department store chain. No comparison. Much better value at Staples.
I can only assume that a big part of Staples business strategy involves making people buy too much of something by overcharging for smaller quantities. I don't need 500 envelopes just 100 would be fine and last me for years but the cost of 100 is [$] while 500 envelopes cost [$]. Even marking them up a decent amount the 100 pack should cost no more than $4.