Regarding the Gacha

It seems that gachas related to events that have already ended cost a bit more magic butterfly stones than the permanent gacha. If you want to pull gacha affordably, it might be best to pull during an event...? Permanent Gacha: Single 300 Magic Butterfly Stones, 11-pull with 1+ SR guaranteed 3000 Magic Butterfly Stones Event Gacha (related event already held): Single 360 Magic Butterfly Stones, 11-pull with 1+ SR guaranteed 3600 Magic Butterfly Stones... I realized there's a 600 difference! I'm still not used to it and there are parts I don't understand, but I want so many things that I'm having trouble deciding...