The appraisers these days are not always bringing in the values that the buyers and sellers have agreed upon. I remember years ago when in Berkeley they were having auctions to sell property. They would put out a price that was clearly to cheap to sell the home and say they would have the auction Saturday at 2 pm. Lots of people would typically show up & the auction would begin. I would watch as 15-20 people would be bidding more than the home was worth and the top bid got the deal. Try to appraise it when it sells for $200,000 more than it was worth yesterday. Better keep track of the other people who were bidding because their is your proof that the market would pay this high a price for a home in Berkeley.
Today is is a different problem in that many sales in the marketplace are falling short of their expectations, not be a lot but by a little. 5-10% is not uncommon. If you have a sale where the appraisal comes in a little low, keep in the back of your mind that all FHA lenders likely offer the Streamlined k product. Change gears and repair something, maybe the roof is older, fix it now, or possibly the carpeting it marginal, single pane windows, change them to dual pane, etc. you get the idea. The Streamlined k can do these kinds of things, even bathroom or kitchen remodels and the appraiser gets to take those imrpovements under consideration with the "after improved" value appraisal. You get that added value and 110% over that value to see if you can keep your deal together.
It is not a "save all" deals program. If the "as is" value falls short of the "after improved value" less the cost to make the repairs you may still be in trouble.