There are presently a lot of out of the area appraisers who don't know the local area and are sometimes making questionable appraisals. I don't want to say more, but any local appraiser will be happy to react on this.
The $ 40,000 addition for the larger yard and a 3 car garage seems reasonable.
I question a comp of a house without a garage in your price range of 400,000-$ 450,000.
Ask more questions or spend the money ( $ 450 ) for an appraisal by a good local appraiser .In the worst case you wasted some $$ ,but at least you know if you paid the right price .
Iam afraid that I red this question too late and it might be a done deal.Let us know how the story ended
If the sales price is a fair market value, and the low appraisal is incorrect, there's no reason it shouldn't be adjusted by way of a new appraisal.
If the sales price is over fair market value, and the lower appraisal is more realistic, then you as the buyer have a decision to make. You can either come out of pocket and pay the higher price, covering the difference from what your lender will lend, or you can take the appraisal to the listing agent and negotiate a lower price.
As soon as the seller sees the appraisal, they will probably want to dispute it right off the bat, especially if their expectations are out of line with market value. After all, it is their home, and they are emotionally attached to it, so "obviously it's worth what they say it's worth." But we all know that's not the truth, and the reality is that their agent is probably relieved that he now has more evidence that the price needs to come down for future marketing purposes, especially since you may be ready to walk away because you can't cover the difference.
They changed the adjustment on both the lot size and the garage from +10K to +30K. The difference between our property and the comps is .29 acre, and no parking vs. a three car garage. This resulted in the 40K adjustment, which is about 9% of the purchase price.