I recently bought a DaLite pull down screen in HDTV format 45X80 High contrast matte white for under CDN $250 with free shipping. (I also bought my projector and cables from this site) In USD this would be under $200 bucks!
I am just finishing up my drywall so I have not mounted it, however a friend of mine has a pull down screen which he tensioned with a bracket near the floor and a bungee cord. Works great.
E-mail me if you want the site with the screen information