make super defense potions from 67 - 91 or 90. which ever level starts using Exteme defs. if i remember correctly its 135xp or 145xp correct me all you like. just my opinion on the guide.
240exp per extreme pot. lantadyme is 5.5k each + the money spent on super def pots is probsbly 2.2k each so 7.7k each
from 90+ herb to get to 99. if you didnt do the super defense method. you will be paying over nearly 10k per pot (extremes)
my opinion cheapest quickest way to 99 herblore. still staying below the 260m mark. unless you got big mills and just do overloads to 99 from 96. (quicker but WAY MORE expensive).
correct if im wrong. this was my method like last month or 2 months ago.