You'll notice that my posts throughout this thread have me flip-flopping between camps. This is not an accident.
The cost approach is not the appraisal. It is a methodology to develop value indications and the result is to be reconciled with everything else that was done (or not done). The hypothical subsititute property is a hypothetical proeprty. We are not holding it out to be a real property that exists as of the date of value.
Highest and best use is not an appraisal. The results are not opinions of value. The models and constructs used in developing HBU are not opinions of value they are the results of sensitivity analysis.