shamelessness as extreme price sensitivity?

The author is saying that price sensitivity is something of which one should be ashamed (i don't understand why the author is saying this, nor do i necessarily agree). The author therefore is saying that loyalty to a particular brand of a product, for what are alleged to be very insigificant reasons is as shameful as loyalty based solely on price.

You have provided good context here, but this is a case in which, to be absolutely certain about what the author is saying, one would probably need to read the entire book, or a major sections of it. However, my sense of the autho's message is that when a particular brand of a product has reached the point at which customer loyalty is only based on very minor differences (matters of taste, perhaps?) between that brand and other brands of the same product, the brand has reached a height from which it can only decline.

The author is further saying, inferentially, that one should be ashamed of selecting a product solely on price (for example, buying a brand because it's cheaper, and for no other reason), and that the same shame should apply to buying a brand solely for reasons of minor aesthetics. One might prefer a particular product because of the color of the product, or the exact form in which it is presented.

I can't see that, though, as shamelessness, because i don't see how that is something of which one should be ashamed. If two products are identical (food that tastes the same, clothing which is just as serviceable and stylish, etc.) then there is no reason to be ashamed of buying the less expensive product. Similarly, if one prefers one product on an aesthetic basis--you prefer the color or the form--as opposed to other products which provide the same value, i don't see any reason to be ashamed because one prefers it for aesthetic reasons.

Without reading the book, though, i can't be absolutely certain that this is what the author is saying.

As Set said, this is really tough. I interpreted it to mean that extreme price sensitivity, to the point that other people would consider it abnormal, requires the ability to ignore the derisive opinions of those around you who would shame you to conform. For example, there are some people who will drive all over town looking for gas that is one cent cheaper than their local station. Most people would consider all that driving to save a few cents as silly or counterproductive.