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Well, the value is gived by investors that trust and use the blockchain tecnology on their projects. Also the versability of blockchain attract more of them to invest on many sectors.
So the relaction id directly proportional => high trust/security/versability = high request/know-how interest = high value.
If tomorrow anyone find the way for to hack the blockchain or find any bugs on it, the value collapse down for the leaving of investors.
Also the unicity of tech at world level give it value.
I'm sorry about my english if the concept explained isn't so clear.