I have Photoshop CS3 on my Macbook that is now a "pro" but I would not have even been able to pay typical eBay price for it; got it as part of a craigslist "pro" hardware/applecare upgrade package.
I bought a sealed Photoshop Elements 4 for my last gen Powerbook; $20 shipped off eBay. Both Mac machines I use Adobe DNG Converter, a FREE download, to convert/upload the RAW images from the camera.
I have Elements 4 on an old Pentium 4, 2.4C PC, and use just Elements for everything (Bridge to convert the RAW images).
Try guess which machines I prefer to do my photo processing on? I only use the full Photoshop/Macbook when I am mobile and "looking" professional; at home I always use the Elements machines.
If you are already computer savvy, with some organization skills, I think anything over $100 dollars is a waste. Every day I shoot photo's, they upload to a new folder in the Photo's folder. I have to create and name that new folder before converting/uploading with DNG, or as I'm converting on the PC.
Lightroom and Aperture do most of the editing corrections a basic underwater photographer uses, creates/names a folder for you I think, and there are some other categorizing /grouping advantages.
For some $200-$250 to help them with organization is worth it, some would go for the full CS4 Design Premium at over $1,000 and Lightroom, while some do what they want/need for; $100, $50, less, free.
30 day trials are available for all the current versions of good software mentioned in this thread.