I think it not so bad because a system like this isn't really competing with primary producers (solar/wind), it's competing with peaking sources fueled by nat gas/oil/hydro/batteries. All of which have a higher cost per MWH. I think too you can do the equivalent of cogen by using the waste heat from the thermal cycle for commercial and industrial heating.

My take is thermal storage is going to become really important once we start taking coal and nat gas plants off line causing the daily power price curve to invert. Power goes from cheap at night, expensive during the afternoon to cheap in the morning and expensive in the early evening. Once that happens thermal storage becomes balance sheet economic.