It varies per level and I can share with you from personal experience from 85-99 doing maniacal monkeys (requires completion of Monkey Madness 2) I was averaging about 600k experience per hour and even more as levels increased. I wouldn't recommend doing chins until you're atleast 85 range if not higher. I would recommend using toxic blowpipe at nightmare zone if not utilizing slayer to help alleviate the cost whenever you do chins.
Note: I was utilizing max DPS gear when doing this method. Void, salve amulet (ei), archer's ring, book of armadyl, etc.