Your friend is the seller, so she is even more removed as a stakeholder than the borrower/buyer. And she has some basis for having a concern.
Here is the deal: Unless the buyer's lender understand the dynamics/uniqueness of the market, this appraisal may just fall into the normal/everyday "assignment" category (which, from what you describe, it clearly isn't).
The problem with an atypical property/market falling into the typical property/market bucket is that the expectation is the assignment can be done relatively quickly and at a relatively lower cost. From what you describe, the appraisal is going to require a fair amount of research and analysis, including going back in time for historical sales as well as going to competing markets and doing some comparative analysis like George Hatch was explaining.
Your friend (the seller) and the buyer have two things to worry about:
A. This sounds like a complex appraisal, and it requires a higher-level competency than, say a tract home appraisal. The lender needs to understand this and ensure that the appraiser is sufficiently qualified and competent to take on such an analysis.
B. You could have the greatest appraiser of all time, but depending on the lender, they may only be comfortable with plain-vanilla collateral. So, despite how well the appraiser can support and explain the valuation analysis, the lender may still shoot it down due to the atypical features of the market.
In the ideal world, this is what would happen:
- The buyer would select a lender that was (a) familiar with this market and (b) made loans on properties that don't always fit in to a nice, pretty picture. A local lender is more likely to fit this profile than a national lender, but I'm not dismissing national lenders; it is just more likely that a local lender will know the market and have relationships with appraisers who are competent in that market.
- The appraiser who is engaged understand the dynamics and challenges involved prior to accepting the assignment; this way, s/he can accept the assignment based on her competency (ability to do a complex assignment) to solve the problem. Additionally, s/he will (or should) quote a fee and turn-time that is commensurate with the complexity of the assignment. From what you describe, the appraisal on this house should cost more than an appraisal in another market where transactions are aplenty.
- Your friend's agent should put together a full package for the appraiser; this includes sale data (closed, active, pending, put on the market and withdrawn, etc.) for this market; a discussion of the low turnover; a comment on how the listing agent determined the listing price, and a summary of the competing offers/multiple bids. If the listing agent (or the buyer's agent) have additional data from other neighborhoods/markets they think are similar, they should submit that too; the danger is that their idea of "similar" is based on price and not physical characteristics. However, good agents should know what an appraiser can consider, and good appraisers are usually willing to accept data recommendations from real estate agents (why wouldn't they?).
- The appraiser, taking all the information s/he has researched, and considering any additional information that is provided to her/him from the agents, will then do the analysis. When it is all done, the value may or may not be consistent with the contract price, but everyone who reads the appraisal will understand how this problem was analyzed and should feel comfortable that the complexities were appropriately addressed. Once more: "appropriate" doesn't mean "meets the contract price". The appraisal needs to support its conclusions based on the market data and the appraiser's competency in completing the analysis. The value is what the value is; if the contract price and the value are the same (which obviously happens many, many times) then everyone is happy! And, if the contract price doesn't match the value, your friend (while not liking it) should be able to see why, based on the data, that is the case.
The more your friend (her agent, the buyer and the buyer's agent) can do to hit the first 3 bullet points, the more likely that the 4th bullet point will be the outcome.
Best of luck!
(For what it is worth, I appraise in the San Francisco Bay Area; including the City of San Francisco. High-density, a lot of transactions, plenty of sales, right? Every now and then, I get the atypical property where the best comparables may be 3 years old or, in one case, 10 years old. For my local lending clients, they understand this and they don't have a problem with it. I don't do retail/large-volume appraisals for national lenders, but they likely would have an issue with that type of property. Naturally, they'd blame it on the appraisal. But as appraisers, we cannot make data up. And that's what your friend is facing; a lack of transactional data. So, to get what is available, is going to take time and expertise.)