Seller won't allow a pre-contract appraisal

[Jocilyn Oler]

I am looking at a property to move my family into for many years (if not permanently) because of the prized location and the desire to live in this area (the exact location actually).  

It is a 1993 4,100 sq ft home, 3 car garage, all brick, and sits on 1.72 acres with two large sheds.  The home is in amazing shape and has never had children in it.  It needs minor upgrading.  The owner's deceased husband was a perfectionist and did everything in a such a manner.  The home is nicely landscaped, but most of the acreage is a dirt field, which was used for gardening and fruit trees.  

I've checked with the city and no flag lots are allowed in this city so the potential to build another home on that land is out.  The seller wants $499K right now (down from an original $529K) and claims $40K of the asking price is due to the large sheds.  I thought you don't include replacement costs of sheds in an appraisal of a home/property??  The comps in the area for similar home and acreage is much lower: $450K and under on all comps.  We feel the home is very overpriced, but the seller completely rejected our original offer of $440K (at the time she was asking $529K).

We asked to pay for an independent appraisal on the home because we are willing to pay fair market value.  The seller said no.  She only will allow the appraisal once the home is under contract. 

My question is:  Appraisals come in higher based on the contracted price (even though this shouldn't happen) right? Any advice moving forward?  I really want this home and property.  Can I structure my offer a certain way to be contingent on an appraisal?  

Thanks!