Casino .bet has been sold for $200,000, OK, but that's NOT a proof that the .bet extension is "still in very high demand."
The proof would be a constant in decent sales (and use) of .bet domains for some time, and that's not the case.
In fact, this extension has never been "in very high demand." Neither in sales nor in usage.
You just have to go to Namebio, to see how many bet sales in .com and how many .bet domains have been sold in recent years. And for how much they have been sold.