Sorry, I might be missing something here but
Isn’t price of energy typically measured in kW hours. Energy = Power x Time.
If a space solar system can output more energy since it stays on for longer, wouldn’t this mean that the cost per watt hour would naturally decrease? This would be because the price of a watt hour I imagine would be Energy / price. So, if our launch cost is a fixed cost, then we would find that E / price decreases.
Very good point: I think the website I linked to refers to peak power, so the Kilowatthours would be lower. (not sure on this, sorry)
If the panels on orbit last double the time and produce double the energy that is only a factor of 4, while the system is about 300 times more expensive. (but again you have transmission losses that I did not consider)