If I'm reading the jp wiki correctly ( https://神姫プロジェクト.攻略wiki.com/index.ph...8C%96#a2d4c6dd ) gem cost should be removed for accessory enhancements around May. I'm playing only for around half a year, but gem cost is the biggest limiting factor in leveling accessories. I don't see the info about gem cost removal on Sanahtling's encyclopedia, but hopefully it still comes.