Doing arrows and selling them for 15-30 gp ea saving you 120-240gp from 290 mana spent, if ever you sit at dp with some ring of healing or mana pots you can create 66 packs of burst arrow, taking at the very least 132seconds (2m12s) spending 19140 mana
lets do some easy maths: 66*8burst*15gp= 7920gp, while require 19140mp/100avg (mana pots) = 191.4 (say 192) mana potions*56gp = 10752gp
if you sell your burst arrow at 15gp you will be wasting only 2832gp per 19.2k mana spent in 192s/3m12s (you require 192 potions at max) now check this table:
Burst arrow price: | balance ea 66 packs |
15gp ea | -2832gp |
20gp ea | -192gp |
25gp ea | +2448gp |
30gp ea | +5088gp |
So basically as long as you keep using mana potions and sell your burst arrow above 21gp ea you will be training mana for free taking you only 3m12s, any higher price will be a slight profit out of it.
Compared to an exercise rod which take you 1m40s to spend 30k mana, this other method require 5m, while could pay waste, require you to keep paying attention to your character during that time and stuff so in perspective:
Method | Exercise Weapon | Mana potions |
Waste | 262.5 gp per second/15k per minute | 14,75gp per second/885gp per minute max could be 0 waste or profit. |
Time Spent | 1000s(1m 40s) for 30k mana | 3000s(5 minutes) for 30k mana but u can't recover enough soul points in 5 minutes. |
Idling | depends on the charges of your wand, the minimun bought wand allow you a 16m40s free time | Require you being there every single second to cast mana potions |
Extra | It doesn't allow you move or perform almost any other action in the game window | You can reduce extra expenses with regeneration item/bonus in the other hand this method require you resting for almost 53 minutes while spending 19140 mana to recover 198 points |
So being fair, the point here isn't if is worthier than exercise weapon, there's no point of comparation are different methods some ppl prefer saving those extra 3m12s rather than using them to make few burst arrow, due is time spent anyway, time that not everyone can afford (specially if you try to do this after th), some other would prefer using that extra time but the fact is: using your whole soul points pool to create burst arrow and selling them in market is a cheap and easy way to spend extra mana and if you can afford the time spent is really worth it.
Source: Soul Points, Mana potion