Another thing, is don't get too attached with their model home. Because in most cases, when you do buy there are so many factors beyond you and your agent's controls.. Example: structural changes to electrical, design, optional plan, these are all planned much in advance by the project managers and the need to change will depend very much on what stage of the home when your contract is signed.
As the other poster said, the home is sold under builders interests, not the buyer at all. Therefore buyer needs to do their own due diligence, does the pricing make sense w standard home, if not walk away.,
What I learnt, the interior of the home is up to the mercy of builders, unless you sign way ahead during pre-selling and only saw the bare lands. The upgrades/layout is the secondary reason why you purchase..Having said that, therefore it's recommended to make sure the location, the neighborhood, the HOA are the best you want to live with years ahead.