Its basically a copy of the previous raid boss event.

80 level normal boss drops 89 starts.
90 level special boss drops 109 starts.
I assume 90 level normal and 80 level special drop 99 stars. So drops would be same as previous event.

First phase has items in exchange shop with total worth of 7k3 stars.
In phase two we will get:
3 more jewelry - total cost 4k5 stars,
Ampies 5 copies each - total 15k stars,
100 level Manyus 5 copies each - total 10k stars,
Gifts 5 copies each - total 5k stars.

Only difference then between this and previous one are the jewelry items, which add 6k stars to total cost.

Overall total cost for everything is 41k8 stars.

With 12 days, 14h worth of "playing", 2 RP per hour - we have total of 336 RP to use.
Assuming one would target only 90 level special bosses thats 36624 stars .
A bit short, but then we will get a better boss at second phase which will probably drop more stars.
This also doesn't include drops you get when you where the one who spawned the boss.

EDIT:

Hehe, was writing this when the guy above me posted his info.