Here's all the loot I got off 112 (4 full inventories) of lobsters (around 18k value on the GE) down at the Roaches.
The total value is 150k (P2P), my last run was worth 132k (F2P) and I'm level 57 att, 55 str and 51 defense.
I spent all but 17 of the lobsters fighting Soldiers and I spent the last 17 fighting workers and drones for filler herbs and runes.
This is the value of the cash-cow roaches, do not fob them off as a waste of time or you will regret it.