The best reference I know (short of an actual bid from a local contractor) for remodeling cost and how it affects the value is Home Remodeling magazine's bi-annual issue on the subject, available free here.
It defines every remodeling job. For example a mid-range bathroom remodel is described as:
"Update an existing 5-by-7-foot bathroom. Replace all fixtures to include 30-by-60-inch porcelain-on-steel tub with 4-by-4-inch ceramic tile surround; new single-lever temperature and pressure-balanced shower control; standard white toilet; solid-surface vanity counter with integral sink; recessed medicine cabinet with light; ceramic tile floor; vinyl wallpaper"
Then it gives you an estimate of what that will cost, in every major metropolitan area of the county (the link is to Portland, OR), AND how much of that cost you will likely recover when you sell. In addition to Mid-Range, many projects also present an Upscale version.
You'll notice that not a single remodeling project will return more than its cost. The best is 91.5% return on a minor kitchen remodel. Of course the monetary return on investment is not the only reason to remodel. If your kitchen was top drawer by 1960 standards, you will get daily joy from one that's upgraded. If you're ready to sell, bringing a kitchen or baths up to date will also make your home sell faster, if not for more money than you put into it.
Take a look at the chart. I think you'll find some surprising numbers. Let us know with a comment on this post