Several ways at looking at it.
Depending upon the cost of the panel. A cheaper panel which is 12% efficient may be more of a value than a higher priced panel which is 20% or 30% efficient.
It's not as if the sunlight which was "wasted" is an expense.
Of course, maintenance and installation costs have to be factored in.
But even on cloudy days they put out something.
I wonder what they might cost if someone other than oil companies controlled the production of them.
Arf