Since I assume this would apply to Slayer, since in bosses you aren't praying 100% of the time anyway (respawns). You don't give me a lot to work with so don't complain. You're wearing: Slayer helm Soulwars Cape Fury Whip Defender Bandos Chestplate and Tassets Barrows Gloves Dragon Boots Berserker/Ferocious Ring For a prayer bonus of +19. While using berserker, your prayer will drain 1 point per 29.97 seconds, or 2.002 points per minute. Assume the player has 70 prayer and is carrying a holy wrench. The player would get 25 prayer points per dose of prayer potion. The player would use 0.08008 prayer potions per minute, or 715 coins per minute. Assuming the player is using extreme potions at level 99 attack and strength. One dose of each costs the player 8648 coins. Let the player repot when his stats have fallen n. Each minute, the extreme potions cost 8648/n without berserker or 7520/n with berserker. But the prayer potions increase the cost of berserker by 715 as found before, making the cost per minute of berserker (7520/n + 715). If (7520/n + 715) < (8648/n), then berserker is worth using. This is true when n<1.75. So basically, unless you're repotting every other minute, it's not worth it to use berserker. We can reevaluate this assuming 99 prayer. The player would get 32 points per dose which comes to 558 coins per minute. If (7520/n + 558) < (8648/n), then berserker is worth using. This is true when n<2.02. So basically, unless you're repotting every other minute, it's not worth it to use berserker. It is probably never worth it to use berserker with extremes.