Ultra Sale's Dewdrop Pack

Dewdrops are super rare, but isn't 20 for ¥11,800 a bit steep? I'm thinking... If converted to diamonds: Dewdrop (8000 diamonds) and Oracle (12000 diamonds) Fate 40 + Oracle 40 = 32000 diamonds Oracle 60 + Taboo 60 = 36000 diamonds It doesn't look good when converted to diamonds... First off, how many days does it take to get them from regular drops? I looked it up, and the probability of a Dewdrop appearing in the 9 regular slots is about 13%. There are 4 refreshes a day (plus 1 with Covenant). If you refresh 5 times a day, there's about a 50% chance it'll appear at least once. In 30 days, that's 75 (around 80-85 with weekly rewards). Let's assume Metatron requires 6 slots for the main attacker and 2-4 for the sub-attacker. If we also make Metatron weapons for other attackers and supporters... let's say 3 Metatrons per color (excluding Heaven/Earth). And about 6 people for Michael weapons per color (rough estimate). If that's 10 Metatron armor slots, 12 Metatron weapons, and 24 Michael weapons, the total Dewdrops needed is 1640. At 85 per month, that's 20 months... ...That takes way too long. I calculated this very roughly, so the actual amount needed is probably much less, but will I only buy the Dewdrops from the Ultra Sale when I desperately need them...?