Lightroom is an excellent program for editing and cataloging your photos. This is the cheapest it's even been.
The Windows and box versions' prices have increased, but the Mac download is still at $70 - and according to the comments the serial number you get can be used on any platform. You'll just need to download the trial from Adobe before putting in the code.
TL,DR: Buy Mac version for $70; if you need a Windows version download the trial from Adobe and use your serial key to unlock.