If you look at housing characteristics you can break them down into 4 basic categories:
Economy is characterized as building a home in the most cost efficient manner using construction materials that more often then not will be cheaper than those used in other categories of homes. If a perosn looked at a catalog of materials used such as cabinets, lighting, flooring, carpeting and plumbing fixtures you would likely see the lowest and cheapest grade used in this category.
Standard this would be a step up from an economy home and a large proportion of homes will come in this category. In a standard built home one may see some construction items that could be found in both economy and custom homes.
Custom you are going to see things that you won't find in either of the above 2 categories of homes. You may see a higher level of finish woodworking, cabinetry, flooring types & selection, granite counters, and stainless steel appliances. These homes are more unique and may may have architectural characteristics that make them more expensive to build.
Luxury this is the creme de la creme of homes and are built with the highest grade construction materials. No expense is spared on anything and have amenities such as landscaping, indoor pools, wine rooms, and home theatres that rival movie theatres and other comparable amenities.
The location of the property also has a great impact on the values, a home located in the best part of town would have much greater value than a similar sized home located in a poor area.
One of the best reasons for looking at the price per square foot is to see what the trends are in an area.