In my own opinion, I don't think it is, I still believe in diamond, atleast the natural ones though. There may be fakes ones out there but atleast when one get the original ones, the value is still worth it. Its a matter of knowing the difference between the two. And no matter how cryptocurrency is taking over, Diamomds will still be among the most treasured value all over the world.
I agree. Diamonds that are synthetically produced can be differentiated from diamonds that are naturally produced.
The rareness of diamonds are what give them a good markup, but then after that, they're priced high for the same reason that pokemon cards are priced higher than a piece of printed paper: demand.
It's a tradition all over the world to buy your loved one a diamond ring for marriage or some kind of anniversay or something. That's a tradition that's not changing. That means everyone who gets married will buy some kind of diamond for their partner. And they'll buy another diamond for their anniversary(s).
It's just like pokemon cards. As long as people keep buying them. They're going to keep becoming expensive.