Disclaimer: The problem with any valuation system is that it assumes that all homes/values are uniform, and that the market is stable as opposed to rising or falling in value. It´s like the old saying that "a broken watch is still correct twice a day" and that the market is at equilibrium at some point both on the way up, and the way down. So many factors affect value beyond 'dollars per square foot': condition, style & arrangement, colors, degree of exposure, balance between prospective buyers vs. available inventory, interest rates, terms of sale, presentation and negotiation skills of the agent to name a few. With that said, the values can be extremely misleading in certain markets. In some states they do not require the sales price to be recorded. In California, they base the property taxes on the sales price of a house and because the property tax information is public, the estimates can be a bit more accurate, however, if the closed sales in closest proximity to the subject property is full of custom homes, the valuation system can be off by $l00,000´s. There are nuances to pricing a property that no beta system will ever be able to duplicate; current trends in architecture and design, lot layout, floorplan, etc. That´s why it´s important to talk to your realtor or an appraiser.