Oh wow, that's expensive. It is really worth the trouble however since rainbowed up gives huge stat boost like they are turning into real rainbow. They also get new abilities too. I have some questions however.
1. Once rainbowed, are there anyway to regress them back in case you want to increase equip slot or skill level with gold skill/dressboom? If not, you might want to max them first before rainbow them up.
2. Can 2*-4* power up all the way to rainbow in this system? (Long and tedious, I know) This way we can lessen the pain of salt further. If not... well silver and bronze are going to get loads of negative outbursts.
PS: Oh and new gacha is great for getting new golds and dupes besides Anemone and Suiren. However getting salt gonna be saltier than ever with 12% rate.