I don't know how widely accepted it is- many do not accept it esp if rote and default use as a formula-
You've never owned a copy of "The Appraisal of Real Estate" have you?
what do you think the 'market reaction' to a needed repair is based on?
Cost cost cost - everyone tries to ignore cost - Sales are a look BACK. Income is a look FORWARD. Only COST is here now today.
The market participants perception of its contributory value.
And they base that upon cost - not dissecting the sales they find on Zillow.
As I asked JG above- You've never owned a copy of "The Appraisal of Real Estate" have you?
in the absence of better evidence, it can be the basis for some kind of seat-of-the-pants adjustment,
That is the point. A - where are you going to find "paired sales" outside a huge metro area.
B - I have seen contracts where money is escrowed to repair certain items to a set max or min.
C- the book (real estate appraisal text books - all of the good ones) will tell you that a cost related adjustment is a real thing. The fact is EVERY kind of adjustment has some sort of caveat or flaw. Trend analysis, Multilinear regression, paired sales. On and on.
D - what flippers and rehabbers do is not an issue. They are bottom feeders to begin with. They also are often specialized in making cosmetic repairs that a home owner would not tolerate. I saw one restretch and deep clean a carpet that I had assumed needed replaced. Didn't look bad but a year later it obviously was not much better than I thought it was. Then they may rent to own and sell accordingly. They pay less, they spend less and they make sure they have a cushion - otherwise they lose their butts.
So perhaps I should ask this question....
How many extractions or paired sales do you need to be "accurate"? If you haven't come up with a fireplace adjustment from negative $5000 to $30,000, then you've not done many such analyses. How many times does a paired sale come up $50, $85, and $70... so is the adjustment $50 or $85 a square foot, or what point in-between? That's $35/SF - an $85,000 difference on a 2,400 SF home. These are dart board adjustments. You can justify your choice as SUPPORT for an adjustment, but not as a true accurate PROVEN adjustment. Ditto C2C. It's not exact, but it is SUPPORTED BY REAL COSTS not adjusted by the whim of the appraiser.
If you say "Flippers typically add 20% to the cost as EP" then back it up. You can't. You won't get a contractor to make such a foolish statement. So how do you defend it in a report nor in a court. The truth is flippers don't use the same metrics we do. Not by any stretch.