The value of CRYPTO coins is determined within the supply-demand balance coming from the users. Just like stocks or commodities, they appreciate or lose value during the exchange based on instant supply-demand pricing. In other words, the more demand a cryptocurrency is, the more valuable it becomes.
CRYPTO coins are stored in the data center of the relevant intermediary institution. The physical money that investors deposit with these institutions to buy crypto money is collected in the bank account of the relevant institution. The danger here is that both the crypto money and the physical money in the bank are entirely under the initiative of these institutions and are managed without any supervision or rule.