From an appraisal standpoint I would not automatically assume the property will reappraise for the same amount as your purchase price. That’s particularly true if there’s more than a couple months lag between your contract date and the close of escrow. Remember, your builder is probably wheeling and dealing with a number of prospective buyers right now and there’s no telling whether your deal is as good as theirs’.
No matter what, a prudent lender will have any appraisal they get under these circumstances reviewed, closely, to ensure they don’t overencumber the property.