You can get up to 1050 points for free in this event, sage cost is around 40-50 points per frag (cant remember, you can check previous event threads with mission mobilization event and dig for picture with ninjas to have exact value). Then, you can buy box with fixed drop of 10points and 1 random item for 20 coupons. While by looking at the points itself its kinda expensive (80-100cp per frag) you will get some of the value back in cave keys, medium refine and medium threads or even a rare ninja (but dont hope for those).