Since so many variables make up the cost per square foot, such as lumber prices, location, amenities chosen, time of year, etc., there is no "standard" cost per square foot. You can get an idea by calling several contractors in your area. However, be aware that their bids probably don't include the cost for building permits, impact fees and construction loans. Be sure to ask them to give you estimates for these items too.
When comparing bids, homeowners should be sure they are comparing "apples to apples." For example, prices will vary tremendously if one builder is quoting an estimate for a kitchen with hickory cabinets and ceramic tile and the other is quoting cherry cabinetry and oak flooring. Consumers should also be wary if the contractor is submitting an unusually low-priced bid compared to others. It's a dangerous situation if the contractor collects from you but cannot pay the suppliers from whom materials are purchased.
We have a new contractor in our valley that has pre-sold 15-20 homes. We have heard through the grapevine that this builder has not charged enough. In fact, not only will this builder not make money on these homes, he will probably lose 10 thousand or more on every house he has pre-sold. Obviously this is going to create a big mess with the lenders, homeowners and the builder. Be selective when choosing your builder.