I don't even remember the last time I bought brown eggs.
When I go to the supermarket, if white eggs are $.99/doz, then brown eggs are $1.59/doz. If white eggs are $1.59/doz, brown eggs are $2.39/doz.
I agree there is no difference in taste or nutrition. Just basic consumer economics.
Part of the reason for the difference in price is that there is less demand for brown eggs. Part of the reason is that brown eggs in factory farm are slightly less profitable to raise due to slightly less efficiency of feed conversion of the heavy breeds that lay brown eggs.