2,453,300 per hour 

45,200 Herblore Inputs Outputs

240 x Poison ivy berries(298,080)

240 x Coconut(1,114,320)

240 x Vial(240)

240 x Weapon poison++ (3) (3,865,920)

Weapon poison++ is made by using cave nightshade on a vial of coconut milk and poison ivy berries. Cave nightshade only spawns inside the Skavid caves and is not tradeable, so the spawn time of the nightshade is the limiting factor in how fast weapon poison++ can be made.

Nightshade location

Cave nightshade can be found in the caves under Gu'Tanoth, east of Castle Wars. The easiest way to get there is by teleporting to Castle Wars with a ring of duelling and walking to the most northern cave entrance, marked on the map to the right. A skavid map and a light source are required to enter. One cave nightshade can be found there, and it will respawn every 10 to 15 seconds depending on the population of the world, resulting in about 240-360 an hour on an average populated world.

Collectors can wait until it has respawn due to the fast respawn rate, which means that you can be afk while doing this.

After collecting 26 cave nightshade (it cannot be stored in a Beast of Burden), teleport back to Castle Wars, bank, and repeat. Once enough cave nightshade is collected, break open the coconuts and put the milk in the vials (or buy pre-made coconut milk), add the cave nightshade to the potion, and complete it with poison ivy berries. Weapon poison++ is often in high enough demand, but it's generally worth it to buy one first and sell for just below that price, as opposed to selling instantly.