"Market cap" as applied to cryptocurrency is a completely fake metric that exists only because it produces viral big numbers. Cryptocurrencies don't have a market capitalization, because they don't represent fractional ownership of any asset; there's absolutely no reason to think that multiplying the most recent price of 1 ETH by the notional supply of 120 million produces a good estimate of the Ethereum network's aggregate value.

Not really. Some markets are. But when NASDAQ100 trade at PE = 30 I do think it is reasonably discounted cash flow under growth assumptions.

But you can trade EU, FTSE100, EM, etc. at a PE range of 15-20. While this is not historically cheap, it is also ont over-rated.