Not Substantial (-50%) aka NSS is a derived limitation (exclusionary accessibility, "insubstantial foes only") whose value is implied by viewing the Insubstantial Only limitation as a disadvantageous meta-modifier which results from an enhancement being combined with a limitation.
That meta-modifier is NOT done via Limited Enhancements since those cannot have negative final costs, only positive ones.
Insubstantial Only -30% (B comes with the +20% Affects Insubstantial enhancement (B102) cooked into it.
This means it's -30% is a net result of applying -50% to that.
This means it should be -60% to exclude substantial targets from something which should normally affect them.
Why this matters[]
Malediction, like "Insubstantial Only", has "Affects Insubstantial" baked into it as well. But it does NOT have "not substantial baked into it".
- due to this, applying merely a -40% discount to this is actually not a big enough discount
- it should actually be -60% for a Malediction to affect ONLY insubstantial foes
Other abilities[]
Aside from maledictions there are a variety of other things like senses which also apply equally to insubstantial and substantial foes.
For example: sight and hearing (they do not need to buy Affects Substantial)
Substantial Only (aka Not Insubstantial) is present (PU8p18) to cover one half of this.
As mentioned previously though, applying merely a -30% discount is too small, because these things do not need to be endowed with the baked-in +20% to affect it.