I am not located in Idaho, and real estate markets are typically local in nature. With that being said, we often see the same thing happening in our area. Often times, appraisals come in for right at the agreed upon price on the contract. Not always, though. If the appraisal comes in too high, then it causes concern to the seller (although they are not always privy to a copy of the appraisal itself). The thought may be, did I under sell? Did my agent give me incorrect advice as to the true market value of the home? Thus, the owner may not want to proceed ahead with the transaction. They may have an issue to take up with their agent. And often it sends a red flag to the lender making the loan. Most loans stipulate that there should be not outside transactions between buyer and seller. So, it's a potential problem.
If the home does not appraise, you know what that means...the lender will not make the loan.
In my experience here, I have seen times where the lender provides the appraiser with a copy of the contract for sale and purchase before the appraisal is done. I don't know what the custom is across the US.
Also, be aware with the overinflated prices we just experienced in many areas of the country, many appraisers were put in very uncomfortable situations. Many fingers were pointed at them later, for appraising homes so high. They really couldn't win, for losing. Now whose fault was it? Buyer, seller, lender, appraiser?
Appraisers have a very, very difficult job, especially in the types of markets we have been experiencing over the past several years! I certainly would not want to do what they do!
An appraiser is probably the one that would best be qualified to answer a question like this.