If it didn't provide value, no one would be using it.
I'd like to introduce you to an entire field of endeavor called "marketing". Non-industrial diamonds don't provide value, yet people are regularly buying them for ridiculous sums[1].
Diamonds do provide value in non-industrial settings, most commonly as an indicator of a person's appreciation for another person. They are in the same value class as cut flowers, although of course at a different price point.
Right, that's why I use heroin.
Lots of people consider feeling good to be valuable. Risk to health is part of the cost that people are willing to pay. Same for alcohol, cigarettes, sugar, skydiving.
This makes no sense. How much you value something is what you would be willing to pay. And they are making money from you in dollars. You just have no idea how much.
You don't pay for everything in dollars. You pay for things with opportunity cost, time, energy, mental effort, etc. in addition to your local currency.