Useful implies nothing but useful. People don't "want" to pay for anything. People want to keep their money in their pockets. They reluctantly pay for things whose usefulness, real or perceived, substantially exceeds the asked price. Gmail is "useful" but I sure's heck wouldn't pay for it.

As for Starbucks, it illustrates my point perfectly:

(1) Starbucks is mostly neuro-marketing. I guarantee you that the buzz people get dopamine-wise from expecting the "reward" of a sugar/caffeine rush is much more important (again, the "idea") than the execution, which counts to about 1% of the customers. I know when I need a quick fix 9X out of 10 I couldn't care less if they got the wrong number of pumps of whatever in there.

(2) To illustrate the value of an idea, the Frappucino was the idea of 1 store manager. Cost: peanuts. Contribution to bottom line: about a billion a year directly, who knows how much indirectly as a "gateway drink" for non-caffeine drinking teens ...

The point was not about the execution, it was a manager thinking, "Within the realm of what we can execute fairly easy, what is a good idea that takes what we can do and adds more value quickly and easily?"

And in the larger context, Starbucks doesn't "execute" anything better than countless immitators these days can; but the idea in my mind is "a special little treat I deserve after a long day." A perfectly executed drink with the same stuff in it just wouldn't make me feel the same if I got it in, say, a sushi place. Again - it's the idea of Starbucks = sexy drinks for sexy people. They're not executing that, I'm imagining it. It's an idea.