Refers to the astonished stare that you assume when taste-testing two or more brands of a particular supermarket-offering and unexpectedly discover that you actually **prefer** the lower-priced store-brand (which traditionally would be expected to have a "weaker 'n' thinner" flavor/texture), rather than a costlier "big name" product.
Being on SSI and Food Stamps and thus having a very-limited budget, I am used to just buying the "el-cheapo" store-brand of groceries whenever I can stand their usually-milder-tasting flavors. Occasionally I do "splurge" and buy the pricier "fancy-pants" foods, though, when the taste is dramatically better, such as Nutella hazelnut spread or Armour Vienna sausage. One startling exception to this latter condition, though, was in the case of Dinty-Moore beef stew as opposed to just the Great Value brand... I bought a can of DM just to try it out in comparison to the WalMart brand, and I had a total case of generic-grocery gawk --- the Dinty-Moore brand was absolutely a-w-f-u-l, whereas the richly-tasty Great Value stew won hands-down! Boy, ya never know till ya try it, do ya???