It only took a few days' worth of AP. Contrast that with the weeks I've spent on Accessory Quests with not much to show for it (and a lot of my own time wasted). But yes, in the end it's just 1% damage and some HP. People have spent more for less, I'm sure.
Magicami Starter Guide: Rerolling for Success
Rerolling in Kamihime Project: How to get FREE SSR Kamihime
Sanahtlig's Kamihime Project Toolbox: Includes damage calculators and other useful tools, data, and info I've designed and collected. Make a copy to edit.