Costing money to produce doesn't make something inherently valuable. It would be expensive to sell iPhones crushed by previously-undriven Lamborghinis, but the product would still be worthless. Neither NANO nor Bitcoin have any inherent value. It's entirely derived from other people willing to pay for it. If people want to use a cryptocurrency, using something that doesn't require 15 GW to power could quite rationally be more valued more highly.