When I was shopping around for illustrator and corel draw last month, I did a lot of "price shopping".
What I found is that most third party retailers that had "good deals" were selling bootlegged copies of the software...something I definitely didn't want. Even some of the more "professional" looking online stores were selling bad copies when I did a little more research and found out what their customers had to say about them.
You can save a few dollars sometimes by going to Amazon or B & H or other large retailer, but I ended up buying it direct from the company website just to be safe.