(In fact, if you look at the photos and video on https://www.infarm.com/vision, it seems like they're already doing multiple layers, each layer with its own set of LEDs; so the energy-usage-per-acre is probably already significantly more than direct sunlight.)
> And also your remark about the energy cost doesn't seem correct, if that were true any kind of indoors agriculture would be too expensive to be possible.
My understanding is that commercially-viable indoor agriculture works by focusing on expensive foods that are not very energy-dense, like fresh leafy greens. According https://www.nature.com/articles/s41586-018-0706-x, the cost of electricity to grow fresh leafy greens indoors is 1% of what they can be sold for. But to grow tomatoes, the cost of electricity is 18% of the selling price; and to grow grains, the cost of electricity is 10,000% of the selling price!