Brand Loyalty. How Much Is It Worth?

It's Just Money wrote an interesting post about ING's 4.15% savings rate, saying that he's happy with ING, thus willing to leave it there and not rate chase. It pushed me to write about something that I've been thinking about for awhile, which is how much is brand loyalty worth? There are many instances we do this...when we shop for Ketchup, do we buy Heinz at regular price or Hunts on sale? Do we buy the Sony LCD projection TV or the Samsung DLP TV? Do we buy the Nike casual shoes or the cheaper generics that look pretty much the same and feels just as comfortable to boot? Do we buy the name brand medicine or the generics? Do we buy Chevron gas or the local "generic" brand? Everyday we face these decisions...how do you decide what "price" to put on brand loyalty? Some people will pay anything to get what they want. Some will buy only things on sale. Now if we got rid of variables like quality and features but said the brand and price are the only difference, would you still buy the brand you like? I admit...I buy Chevron with Techron gas instead of the local "generic" gas even though I'm not sure if Chevron is really better. I guess marketting works! I buy Heinz ketchup even if Hunts is on sale. I like the Heinz taste. I also moved my money from ING to HSBC even though I like ING. There are some "mystical" value that I place on these things. Funny thing is I can't figure out what and how my brain figures out these "mystical" values. I do buy generic drugs though, and I would buy a Samsung TV even though I'm a big Sony fan. Then there are many things that I just buy without any brand loyalty and just look for the lowest price...Am I crazy? Am I being irrational?