[ChuckMcM]

It becomes entirely a brand thing and is the original value proposition for brand names. By offering trade mark and trade dress protection for brand names it allows a manufacturer to make available test results, and to periodically inspect/test product for compliance with those results, so that the customer's expectations will be met.

These days people buy the "kirkland signature[1]" product and two things are true, the person most responsible for putting that product on the shelf in front of you is motivated by cutting manufacturing cost and maximizing profit above all other concerns, even whether or not the product resembles at all what the packaging says it does. They are not aligned with your desire for a quality product.

If you are a discerning customer you will find that the actual ingredients of, and quality, of a product with a house brand varies from state to state and year to year. That is an effect of the 'buyer' shopping around a contract to manufacturers, domestic and abroad, who will maximize their profit.

Of course that doesn't mean that if you buy a "brand name" that you are getting the best product. But at least the manufacturer is invested in the quality when it has their name on it and reasonably aligned with the consumer's interests. That goes out the window when it is someone else's name on the end product.

[1] This is the CostCo "house brand" for products they have sourced through a variety of manufacturers.

[brownbat]

As a counterexample, Kirkland Signature's extra virgin olive oil fares really well in independent lab tests, while still being low cost:

http://www.laweekly.com/restaurants/best-bargain-extra-virgi...

But you're right, brands are supposed to promise consistency, not quality. A McDonald's burger should be basically the same at any rest stop, that's one of the reasons they took off. Some brands don't even offer that though.