The paper does contain (rough) cost estimates, specifically the cost per unit of energy storage (about $13/kWh) and the cost per unit of power (from $0.20-0.27/W depending on the choice of gas.) See section V, "Cost".

I'm not impressed with the costing methodology used, but it's probably at least in the ballpark.

Here is a framework for government backed research into the topic: https://www.energy.gov/energy-storage-grand-challenge/articl...