To add to what the other agents of told you below, you also need to keep in mind that taxes shown on the properties you are looking at are what the current homeowners are paying, and that you could be re-assessed after your purchase. Right now, taxes are supposed to be based on the 2002 base rate. There is much controversy reagrding that however, and on occasion the disparity may simply be that different homes were assessed differently. Also, many people take the homestead exemption which lowers their assessed value as well. Sales price here in Pittsburgh generally has absolutely nothing to do with the assessed value, and that is perhaps the number you want to look at. Your annual taxes will be 2.941% of your assessed value if you are in the City of Pittsburgh School district.
I hope that helps!