The press release contained current and next years prices - 200$/kWh @ 8hr storage is the current cost of flow storage.

Its not really sensible to price 24hrs of li-on storage considering li-ons charge/discharge rate capability is fixed. There is no use for the capability to charge and discharge 24hours of power within a couple of hours, but you cant avoid buying it with li-on. With flow batteries you price the discharge rate and the capacity separately. This is why flow batteries should work out a fraction of the cost even at todays price.

I would rate the reliability of a battery press release slightly higher than a signed-off budget and timeline for nuclear construction.

And when it's press from a battery maker, rather than a battery researcher's university press department, the battery press release is far far more reliable. I'd say their cost overruns will be at most 20%-30%, compared to nuclear's usual 200%-300%.