Ryan Carson, over at Carsonified, has graciously posted the costs of producing his web app, Dropsend, as well as the financial figures behind four other companies: FreshBooks, Maya's Mom, Mobissimo, and Wesabe. Better yet, monthly maintenance costs are provided and broken down into categories.
Very valuable stuff.
It's a PDF, so it may wreak havoc on your browser.
http://www.carsonified.com/sxsw.pdf