That is not true. For real cryptocurrencies, like Bitcoin or Monero, they are live when there are at least two people using it ( sending transactions) and there is at least one guy mining it. That si it. It dont need to have any specific USD value to work.  For tokens is differently. They rely on some other asset platform, so dont need any miners. Bit most of tokens are or securities or utility tokens. OK a lot are basically nothing and are totally useless. they are dead. But these utility and security tokens are linked to one project, that at least for securities have little to do with blockchain. And these are dead when that project is dead. Usually it die when they run out of ICO money and since they are some fancy rich bitches, no one of them would work for free liek Bitcoin or Monero developers work.