Cryptocurrencies will IMO always have some sort of residual value simply because of their usability for illicit activities. The specific value is debatable, but I'd guess a "round" number will be where psychological effects will naturally converge towards.
I don’t think these activities need a specific value, they can pay for a hedged position or just be fine with funding/withdrawal slippage tax (provided that exchanges are still functional). Also are you sure that psychological effects naturally converge to anything at all on the crypto market or in general? It’s usually strange attractors all the way down rather than a stable point.
It must be hard math, soft science and such. Definitely!