Totally depends on the airline, the company i work for makes its money mainly from the front, but our main competitor from the back, our highest config 744 is 14/38/30/269 but most of the fleet is 14/70/30/177 so nearly 40% premium. The other companies lowest config has more seats than our highest, so thats why their fares are sometimes lower because more Y seats to fill. Full fare econ is a money spinner but the discounted rates are nothing more than cost covering.