An appraiser's job is to estimate the market value of a property. Here is the definition of market value;

The most probable price that a property should bring in a competitive and open market under all conditions requisite to a fair sale, the buyer and seller each acting prudently and knowledgeably, and assuming the price is not affected by undue stimulus. Implicit in this definition is the consummation of sale as of a specified date and the passing of title from seller to buyer under conditions whereby;

1. Buyer and seller are typically motivated
2. Both parties are well imformed or well advised and acting in what they consider to be their best interests
3. A reasonable time is allowed for exposure on the open market
and so on.

I can come appraise your house for $2,999,999,999, but just because I say it is worth that much, doesn't mean it actually is. On the flip side I can appraise your house for $1.99. Would you be willing to sell your house for $1.99? or would the typical buyer want to pay $2,999,999,999 for your house? Don't think so. This is where the buyer and seller set the market. Market value is what a typically motivated buyer will sell his house for and what a typically motivated buyer will pay for the house. The appraiser just reports this data. That is it. You are over thinking it.