I've found that collecting Mort-Myre Fungus Earns about 400k Cash per hour.
Even more if you have a Beast of Burden.
Levels needed:
Here's How:
Wield Silver Sickle (Blessed)
Light Gear
Inventory:
Empty!!! except for 20 dust runes and 20 law runes--- For HOME TELEPORT
This assumes that you have a Kharyll Portal and any Alter at your house.
You Spawn the fungus, by operating your Sickle. Then collect the fungus that appears, which is worth 1k-1.1k ea, it drains your prayer by 'casting bloom'.
After full inventory, you should have between 7-20 prayer points left (with 70 pray).
You teleport to your house and pray at your house alter to restore points. then exit through your Kharyll Portal (Canfis Bar). Bank at Canfis bank, and run back to the mort-myre swamp gate.
Congratulations! 400k per hour!