People being paid by the hour is just a result of simplifying work, in the very past everyone was a merchant and they sold their goods/services.

The same old behaviour should be applied to machines, it doesn't matter how much resource a machine takes to do the job, what is important is the output. The pay should not be X*Watts, but X agreed in advance for training that specific neural network, this type of market incentives evolution, where the machines that can do the same job with lower resources have the lower hand