Reciprocal Enhancements are named after Reciprocal Advantages but given Counter Disadvantages uses a totally different mechanic they should not be called Counter Enhancements..
Instead of being an advantage based on buying off a disadvantage, they are enhancements based on buying off a limitation.
The first example of this in the books is explained on GURPS Fantasy page 130 in the blue box for Restructurable Magery, when it explains how the Limited Enhancements rules are applied to a Reciprocal Enhancement (effectively "Not Divided Magery" or perhaps Undivided Magery, layered atop the Divided Magery limitation, rather than modifying the limitation directly.
- Divided Magery is a -40% limitation on levels of Magery.
- But then not having the limitation is effectively an enhancement.
- For example, not having Divided Magery is a +40% enhancement.
- Buy this enhancement with some level of Preparation Required.
- For example, if it takes 8 hours to restructure Fatigue points, this is a -60% limitation.
- Taking -60% of the base +40% gives -24%.
- So where Divided Magery is -40%, making it Restructurable in 8 hours reduces it to -24.
This concept is the basis for Either/Or Limitations
Comment[]
This seems to have be overruled by later works where percentages are additive not multiplicative.
- Power Investiture: Magery (Functions as a Different Talent ±0%; Sanctity Replaces Mana: ±0%; No Zero-Level Requirement +10%; Inspired Learning +20%; No Spell Prerequisites +30%; Pact -10%; No Magic Item Sensitivity -20%; Limited spell list -30%)
So removing Pact -10% from Power Investiture would result in Magery with a +10% modifier and no Magery 0. So this form of Magery 1 would cost [11].