I don't think that there is a discount for Premiere Pro if you already have AE and Photoshop, etc.
However, there is a cross grade discount for Final Cut owners. http://www.adobe.com/products/premiere/switch.html?sdid=KAEVG
I am using the Creative Cloud for $29.99/month and I am very happy with it. I get all of the software I could possibly use for video, pictures, web sites, etc.