Whereas you can whip up close to a 2-pound batch for under $2.50 (and less, if you catch a good sale, or happen to have an Aldi's in your neighborhood), the packaged variety will typically cost $5 or more per pound. Making it yourself represents big savings. Big flavor, too.
Those prices are absurdly expensive. I can still remember the first time I checked it out in the deli department. I think I dropped the package I was holding, I was so shocked by how much they were charging.
And it really only takes minutes to put it together in a food processor or blender.