I'm also confused about how people think and talk about the market cap. My sense is that the total economic value of bitcoin holders can't be much more than what they have collectively put in as dollars minus what was spent on mining, which is only a fraction of the market cap. If it's more you get a weird kind of inflation where it's not a central bank printing money, but where "value" seems to spring out of thin air just because the masses are attracted to bitcoin (with FOMO as the main reason).
I can't quite wrap my head around all of this. I've been interested in blockchain for quite a while and have been keeping up with what's going on, but many things about the cryptocurrency market just don't make fundamental sense to me. (Another example - Ether basically being the denomination for transaction prices on the Ethereum network, meaning the higher it's priced, the less useful the network is, which seems like a conflict.)
I'll keep paying attention and see if I can learn a thing or two about real world (irrational?) economics.