I'm doing monkey madness service for rs cash or some paypal cash.
400k a quest or 2$.
I do the puzzle, you just have to make sure your account is able to kill the demon. 1 defence or 1 pray isn't bad, but it needs at least 53 magic / 60 ranged or a cannon. Some food is required too, ( like 170 lobsters and 40 sharks) and some anti pots and rings of duelling come in handy too.

I do the first one for free, to prove i'm capable of doing Monkey Madness