[sboselli]

If BTC has any value at all, then all other cryptocurrencies have at least some minimum value solely as a possible redundacy or replacement in case of emergency.

That's not the whole story though, some of these other cryptos also serve as a testbed for new concepts & improvements, differ in particular ways to better suit a specific purpose, target different markets, have different core values or are alltogether alternate technical implementations.

Each one of those nuances adds some deegree of value. As with any stock or other economic asset, their price today is not necessarily reflecting the value it has for practical use today, but rather the possibility that it will become necessary or more dominant in the future.