I definitely believe an adjoining owner can have a greater interest than a buyer who is not, but nearly every property has adjoining owners (save for those who own their own island), and I believe they are part of the market.
I'd have to agree. I don't quite see how you can ignore those sales typically, save for access or some other consideration as you mentioned.
My question stemmed from dealing in farm appraisal and encountering sales to adjoining owners fairly often. Auctions certainly display that kind of competition at times, but I believe that is the market, too. If you've seen aggressive competition like that which might tend to create a wider range from other market sales, and you use those sales in another appraisal, do you ever include but set them aside as outliers from the "bell curve"?
You keep saying part of the market - that can become a weasel word, which means everything is a comp no matter the terms of sale or odd, atypical motivations of the parties.
Market value (I am sure you know the definitions) takes place under a defined set of terms and conditions and buyer/seller motivations. Anything outside of that, while it may be part of the market, is not a transaction that represents market value; thus, it is typically excluded as a comp.
Market value is also accompanied by a market exposure estimate ( number of days, weeks and months it needs to sell at the MV price in the appraisal )s.
A sale of an adjoining property to the neighbor is either nonarm length or too atypical in motivation to qualify as a market value term transaction. A lot next door to Mr Marshall Jones who lives adjacent, can have a very different value and use particular to him, than to every other buyer in the market .
MV is predicated on the thousands or hundreds or scores of other possible buyers on the open market, not just on Mr Marshall Jones next door. He is an outlier, atypically motivated buyer. He did not purchase the property because it was on the open market ( typically) he purchased it because it is next door and either he approached the seller or the seller offered it to him.
Saying everything is the market, and who cares if it is sold at MV terms is a form of cheating. For example, a sports game (basketball, football, tennis, etc.) has a defined area and a set of rules and regulations and violation and time penalties. Heated arguments, the referee, a game won or lost over a foul .line. Without those rules and limtiaiotns, it is not the sport, it is a a bunch of guys ( or girls ) running around with a ball.
The rules and regs that define the sport,, just like the "guideposts of the market value definition, define Market value
If you are not doing a MV appraisal then you may be free to use the other sales. This is why we have a definition of value in an appraisal.