I see your point with it being a cost efficiency issue.... However, I noticed that they’re claiming that it produces 70 watts from a concentrated 230 watts.
That’s 30.4% efficiency, a remarkably high efficiency for solar cells. Are these Gallium-Arsenide cells? Those are the only ones I’ve ever seen break 30%. But they’re danged expensive, so minimizing the amount used would be critical.
The other thing that I don’t remember a thing about that I wonder with this is what the effect of temperature on efficiency is on a typical array. The best of both worlds would be if concentrating the sun reduced the amount of cells you needed, and the cells used would increase in efficiency at a higher operating temperature.... You might need to cool them, still, but like a car engine, which runs best at a careful balance well above ambient temps....