Yes, but I just want to mention demand in this context isn't adoption of cryptocurrencys, but demand to own them. For example if we were talking about a stock, Tesla's stock price may go up because of increased demand for the stock, but that isn't necessarily because there is more demand for Tesla's products, although a predicted increase in future demand could be what investors buying the stock are betting on.
Also, at this level demand owning crypto only makes sense if it's undergos mass adoption fairly quickly. I believe Bitcoin has a market cap of around 3 or 4 times that of PayPal, so that's the kind of mass adoption we'd be talking about here for current prices to make sense.
I'd believe the 15B is transaction volume (including investors buying/selling) not payments for regular goods?
I am doubtful anyone is actually holding and transacting on clear market with BTC.
Speculators believe the value will go up, so they buy and hold the asset. Each individual's timeline will vary, some will hold for a few days, some will hold for years or forever. But ultimately the price is determined by buyer demand and supply (or lack thereof).
Coin prices are high relative to its recent past. At $1k people though Bitcoin was expensive. $5k, $10k, $15k, same thing. We won't know what the true price is until we the bubble pops and the mania stops.