Seats 18A,B,J&K are in my opinion the best Y seats on the aircraft thus the preferred payment option. I have flow TATL and TPAC in the this row and have been able to sleep quite well. There is ample legroom to put your bag on the floor as a foot rest and just hit the bulkhead with your feet (assuming you're not 6'5"). If you are not AC E or SE you will need to pay. Something to consider if you're looking for comfort.