> Price's law states that the square root of the number of people in a domain do 50% of the work. This means the number of "useful" people increases linearly with size but the number of not-so-useful people increases exponentially.

Assuming you mean that the smaller group accomplishing half the work is "useful" and the larger group also accomplishing half the work is "not useful", it certainly doesn't mean that.

It means, very clearly, that the number of "not useful" people increases linearly with size, and the number of "useful" people increases sublinearly. But even if your definition of "size" included only useful people, x^2 is a polynomial function of x, not an exponential function of it.