On the MLS sheet the Market Value is the tax assesment value. The purpose of showing this number is to let potential homebuyers see the number the property taxes are calculated by. Keep in mind in Allegheny County, this will change because of the reassesment under way.
You also need to know when the county last valued the properties. In my county the last county-wide evaluation was 12 years ago. Thus Fair Market Value on our forms is 12 years ago! You cannot price a home using this figure. It's used for taxation purposes. You need to find current comparable sales in the neighborhood to answer your questions -- what is fair market value NOW for the house?
The MLS in this area puts the appraised value in as the market value. This is something agents have no control over. All buyers should go over one of those info sheets with a local realtor to make the information more useful and in some cases downright confusing. Any other Questions about our forms?