I don't disagree that something about the equation has to change. I think that "thing" is the 0.17 acres. According to this webpage[1], the productivity of a vertical farm is 11x greater than a horizontal farm.

But, that said, I don't think a complete replacement is necessary for this to be significantly beneficial even on a subset of grown plants.

[1] http://stateofindoorfarming.agrilyst.com/