Assume enough energy is supplied to charge the batteries. So lets say we want 1kWh during 4 hours, that puts our capital cost at 4 kWh*200$/kWh = 800$. Now we assume this system runs every day for 4 hours during ten years. Ten years sounds reasonable, but it could be less. 7 years maybe? So about 1kWh*365,25*10=14610kWh in total. That gives us 800$/14610kWh = 0,0548$/kWh or 54,8 $/MWh in 2030 if I didn't make a major mistake somewhere and assuming no efficiency losses. That's pretty good.