Realtors have access to true sales data housed within the MLS, which is also completely private to non-members. This data is what we use to provide you with a much more accurate analysis of the market in your area, and thus help determine a fair property price.
Trulia and Zillow on the other hand simply scrape data from random public sites since they are NOT connected to the MLS, and their "guesstimates" are usually quite far from being accurate. If you'd like to receive a market analysis on any specific property, please feel free to contact me at your convenience and I'd be happy to assist.
Diane Briggs, REALTOR®