Every year, Remodeling Magazine publishes the Remodeling Cost vs Value Report. You can now view the 2009-2010 Cost vs Value Report here: 
2009 was a year of transition for the remodeling and real estate. One would have thought that the costs for remodeling projects would have fallen, but that turns out to not be the case, although the rise was smaller than in previous years. On the other side of the coin, even though costs increased slightly, the value added of the projects dropped slightly. Of courses some of the difference could be the result of consumers sticking to projects that are “back to the basics”.
According to the report, for now, it looks like “Bling is not the thing.” The four-year Cost vs. Value trend toward smaller, low-maintenance projects and an emphasis on essentials over extras will likely continue to influence homeowners remodeling plans. Exterior improvements were more common, primarily because exterior improvements contribute to the overall look and feel of a building. In other words, in a market where there are more buyers than sellers “curb appeal is king.”
For the San Francisco Bay Area, improvements that increase a home’s value above the project’s cost included, adding a bedroom in the attic, a new deck, new entry doors, kitchen and bath remodels and window replacement.
The report provides data on a national, regional and local level for easy comparisons.

