If you only want one app, you can generally subscribe to any of the majors for $19.99 a month. Once you get past two, however, it's not worth the ala carte method.
I looked at Creative Cloud when I needed to get my own copies of Photoshop and Illustrator for web design. I didn't need any of their other apps. I ended up buying the boxed CS6, Creative Cloud's "all or one app" approach is not flexible enough.