Benefit and cost to whom? If I use your definition and apply it to individuals, that's exactly how money works. If I'm willing to pay for something then it must have more value to me than the money I am paying, otherwise I wouldn't pay for it. So if people are paying for crypto or crypto services then those things must be providing enough benefit to be valuable.

To the parties involved. I think the question is -- what is the value to the party buying cryptocurrency? Outside of gambling, that's not clear to me. Which is not to say there is no value!

> If I'm willing to pay for something then it must have more value to me than the money I am paying, otherwise I wouldn't pay for it.

I disagree. People pay for stuff of no value to them all the time, for various reasons. That someone is willing to pay doesn't automatically mean it has value to them, although it does heavily imply it.