Lots of things have a cost, and lots of things are difficult to manipulate. Bitcoin has value only because of speculation and the Greater Fool Theory. There's nothing fundamentally distinguishing BTC from any random shitcoin. Why is Bitcoin Cash worth so much less than vanilla Bitcoin?

It's very difficult for many folks to accept this, but the difficulty of producing something (mining) does not determine its economic value: https://en.wikipedia.org/wiki/Labor_theory_of_value