The job of the appraiser is to write down a number as large as or larger than the amount to be financed. They know this and they know the number in advance. What they do is not rigorous.
I paid a couple hundred bucks for an ex-general contractor with a thick binder to inspect my house for hours, looking inside the furnace heat exchanger and testing every wall outlet and inspecting the plumbing and roof inside and out and insulation and foundation and everything. That is a detailed analysis of what you're likely to spend on maintenance and upgrades over the next ten years. Its probably more useful than an appraisal but it takes a lot more time and money.
http://www.freddiemac.com/loanadvisorsuite/loancollateraladv... http://www.freddiemac.com/loanadvisorsuite/faq/loancollatera...
This doesn't even take into account the process for appraisal management companies (third parties).