The standard price of Adobe Photoshop CS5 extended is normally $1000, while students can get it for $300. However, Adobe is now running a promotion so students can get it for only $40. It might be worth buying Photoshop in one of Adobe's "Creative Suites", such as Web Premium ($90) or Design Standard ($60).
You will need to provide proof that you're a student, and you'll probably need to enter the following coupon code before checkout: SAVE80EDU
Adobe Discounted Software
Although the deal was supposed to last until March 3, it is now expired. Adobe says it was a pricing mistake. Its unclear if they even honored the deal for those who purchased it before they fixed it.