And why is Photo shop pro over the top in price?
Mostly because Adobe has a very large market that relies on their proprietary product, so they are able to charge users an arm and a leg for the software that they "need".
For creating web graphics what would be the best choice?
Adobe's photoshop is pretty much the best solution for graphics editing, as far as functionality and usability go: but, if you can't afford it(you certainly wouldn't be alone), then the best choice for you might be a comparable, free solution like GIMP. Furthermore, if you work as part of a team, and everyone uses photoshop, then the best choice would be photoshop so you can integrate with the team better.