User blog comment:ClariS/FEEDBACK! Cost Efficiency/@comment-4743916-20130201012211

I think that for big items the most expensive raw stat item should be used to calculate the cost efficiency while smaller items it's ok to use the lowest tier raw stat item of its kind.

For example, it'd be ok to use longsword's price of 400 for 10 atk damage for something like hexdrinker but for maw it'd be more appropriate to use BF sword as the cost of attack damage.

There is an added amount of cost efficiency for buying a bulk of stats in one item similar to how it's more efficient to buy large raw stat items instead of smaller ones.