Cryptocurrencies are not actually a "currency". They are far more like equity than a currency and an equity valuation model isn't inappropriate.

For a start, "currencies" are used to measure value independently of their monetary base. For example, if a regional authority is in the process of commissioning an estuary bridge which takes 4 years to build, it will create work in progress entries in its books which will be monetised by credit markets at discrete points to keep the project financed. (This is the 'creating money out of thin air" aspect of currencies)

Crypto, on the other hand, is simply an electronic asset which markets have decided to endow with tradeable value - the only difference form a peice of rock being that it can travel through wires and therefore can be used to directly exchange for goods and services as if it were 'electronic currency'. That exchange is actually barter because instead of being carried out in abstracted monetary units who's denomination is independent of the material of the trade, it's simply a straight swap.