Botting crabs doesn't make money, or does it? Why not train your main while earning back the price of the script and more?
PKers don't like to PvM, so they will pay good money for a ready made account.
A single account can be made in a week and will more than pay off the price of the script.
A $20 account can be made in under a week of botting, see these accounts for sale.
As long as your account does not have any black marks, whether it's botted or not no one will know, and in fact most people expect accounts to have been botted on.
Some people want their own accounts trained, in which case they will pay premium prices for fast training.
Prices range from 10gp/xp up to 40gp/xp depending on the account build and current stats. If the account is a pure, prices are higher. On average you can expect to earn upwards of 2m/hr!
When a service is botted, people typically pay half, however it's almost zero effort so it's still worth it.