Limitation for "requires human sacrifice"?

[RogerBacon]

Let's say I'm creating a summon demon spell as an "Ally always available, summonable, minion, unusual powers" and I want to put a limitation that it requires a human sacrifice (illegal, risky, etc.) What would be the limitation's value? Would the price reduction come after figureing the total cost of the summons? If not, it would hardly have any effect since the "summonable" alone is +100%.