[citation][nom]supertrek32[/nom]Check out GIMP....and it has the best price of all...[/citation]
GIMP is a great piece of software, but like another said, it's incredibly clumsy. And it also doesn't support many of the huge features that artists have come to rely on in PS like GPGPU functions and many tools that do extremely long and tedious tasks in seconds.
But PS is just one aspect of the Creative Suite. You're forgetting about Illustrator, Acrobat, Flash, Dreamweaver, and fireworks, all which are nearly required to do professional web development work in a truly diverse environment. I also have friends that do Video Editing, who couldn't live without Premiere pro, but could certainly live without the pricetag.
Also, since Adobe has such a stranglehold, almost all game asset texture exporter plugins are configured to work only with photoshop. It's a huge PITA.