Make sure you pray fast and ensure that you shield yourself from the effects of magic. When you are ready, turn them on and then use the spade. Zamorak wizards will pop up. They will be able to chit. The rune crossbow is a weapon that can kill any wizard, barring the final one after you've defeated them all. Then, spam dig again. After that, you can go back to the chinning.
The cost:1 45 death drop pays for 30 Chinchopsas. It is likely to take 1 prayer potion per month to keep them alive, which would be enough to kill about 20 wiz