User blog comment:Sasha Dawg/Mod Idea: Soul Collecter NPC/@comment-97.117.164.113-20120722235404/@comment-5305702-20120723173019

She should sell different Souls at different value, because some souls she will be selling are dropped by Hardmode bosses and each of them has different difficulty at defeating.

For example, Souls of Sight which are dropped by The Twins, which is the easiest Hardmode boss, should be sold for about 10-15 Gold Coins, but Souls of Fright, which are dropped Skeletron Prime, the hardest Hardmode boss, should be sold for around 40-50 Gold Coins