[Noxid]

I would have to weigh on the side of keeping murai sinks in the game. It's not too hard to just have it passively build up over time without you even selling things. Also the average player is only gonna ever upgrade a handful of 10*, cost is only an issue when you are pumping out lots of new characters and the types of people who do that generally have plenty of money to spare so this along with hikari stamps drains money from "veteran" players.