Thank you for the responses, it's greatly appreciated. I have appraised many proposed SFR dwellings for "spec" construction financing where the cost breakdown provided (including builder profit/overhead) was significantly less than the SCA. This is much easier to reconcile than the situation surrounding my initial post.
This report was based on the hypothetical condition the new (2021 model) MFG home was installed on the borrower's 5 acre parcel. After extensive analysis and reading multiple articles on EP/EI I came to the conclusion the variance in the SCA and CA is reflective of time and risk. I could purchase the same MFG model at the same price, buy a similar 5 acre parcel listed on the MLS, pay for site prep, permits, etc. The time involved dealing with the purchase of the MFG, permits, obtaining bids/hiring for site development would be of value to me, as I can generate income elsewhere instead of spending the time required to facilitate the project.
Does someone need to be an entrepreneur to receive the benefit of EP/EI? My conclusion, absolutely not. If a person purchases a house for $250k and sells it a year later for $325k does that make them a RE investor? In my opinion, no; however they would receive the same benefit as a RE investor, which could be considered EI/EP.
Again, this report was based on the hypothetical condition the MFG home was complete, resulting in the SCA utilizing completed "move in ready" comparables. The variance between the CA and SCA is appears to represent time/risk. The market is willing to pay a premium for a ready to move in MFG home, instead of spending the time and incurring the risk of facilitating the same project. The motivation of the borrower may or may not have been to gain equity (EI/EP) by taking on the risk of construction, however this was the case based on market data.
The intended use of the appraisal was to provide an opinion of market value based on the HC all items were complete, therefore the SCA was considered to be the best indicator of MV. This appears to negate the principle of substitution of which the CA is based on...so should EI/EP be included in the CA when the SCA provides adequality supported data there is a market reaction? If so, then in theory the CA should always equal or exceed the SCA depending on market conditions. I do not complete the CA in this way, however I believe the theory has some support...