Average screw cost when not guaranteed, assuming Akashi is Kai and not counting any equipment cost :
[[File:Average costs.png|750px]]
[[File:Average costs.png|750px]]
−
Screw cost increase when guaranteed :
+
Screw cost difference when guaranteed :
[[File:Scew costs.png|1500px]]
[[File:Scew costs.png|1500px]]
+
+
As expected, when the guaranteed cost is too high, not guaranteeing the upgrade is on average cheaper screw-wise, but this is not counting any potential equipment that may be lost and so may imply a higher screw cost.