From levels 61-99 it will take 1,273,215 headless arrows tipped with adamant arrowheads. They give 10exp/arrow with 36,000 max made per hour. (360k exp/hour) Each arrow costs 149 coins to fletch, resulting in about 5,400,000gp loss/hour. If you want a better way, just do broads, it will cost a little more per hour but it is much faster.