Here is the rough cost in coupons to get the event points to buy one of the items and the average cost for that same item over the last 4 months

2 events you can spend coupons on, Mission Dealer Boxes and Summer Event Badge (both for 20 coupons each)

Item - cost - (average cost in recent events)

Ninja

Hanzo Salamander - 70 - (91)

Hinata Dreamworld - 50 - (57)

Masked Man - 176 - (177)

Hidan Death - 200 - (223)

Gaara 5th - 70 - (69)

Kushina Uzumaki Habenero - 110 - (175)

Items

Cave Key - 14 - (21)

Charm Materials Pack - 110 - (119)

Summon Scroll - 60 - (58)

Mount Myoboku Gift - 12 - (12)

Wild West Clothing - 60 - (60)