My take on this is as an appraiser we are paid to mirror the market.
If your particular market participants utilize that method of valuation in the buy/sell decision, that approach should/must be included in the appraisal.
Developing approaches to market value by methods not utilized by active market participants in your marketplace is an academician exercise.
I understand what you're saying but disagree. GIM (or GRM) analysis is simply another tool in your toolbox to help you produce a credible valuation. Given the type of sale data you have, some tools are better than others.
Except for institutional investors, few participants use DCF analysis, yet I see that all the time!
And do you see many buyers gridding out sale comparisons and making adjustments for gross building area, financing concessions and the like?
Aside from brand new buildings, who uses the Cost Approach?
I know some investors that make the buy and sell decisions on nothing more than gut feelings. In fact I've seen it often enough, that I begin to question the usefulness of thoughtful analysis to these participants.
But how would it look if, in an attempt to mirror the market, I used this approach in a report?
The thing about markets, many of them anyhow, is that they are not monolithic. Healthy markets have buyers, sellers, investors with a broad range of motivations and inputs.
Thank God, too! If markets were monolithic, AMCs could simply run algorithms to solve for value. Where would that leave us?