To clarify — products (almost any discretionary one)will be purchased based upon the perceived personal value of it. In many cases, that perception is based upon some pre-defined personal bias (I don’t buy from that store, or in the case of books, I don’t buy eBooks, or more specifically, I don’t buy $1 ebooks, etc.) — and each person has an almost unlimited number of bias filters. At some point, we will reach “value” as a filter — some people will perceive a $1 ebook as less “value” than a $10 or $20 ebook, regardless of the subject matter. Some will see it as an opportunity to read something new (they like to discover), to each, they filtered based upon their personal value bias — which can be “created” from so many sources, it’s almost impossible to determine.
A $5 coffee? Potentially there is something of higher value than just the coffee to that person. A $10 cocktail, once again, it may have nothing to do with the cocktail, it could be the social atmosphere, or the gathering of friends, or any number of “value” triggers involved.
How each person individually spends their money has more to do with their psychological makeup, and on a macro scale, their attachment to society in general.