I will say that OS X, especially 10.9, is great at consuming RAM. Whether it's a feature of the OS to use as much as possible for better performance, I find that with the 8GB of RAM in my laptop I only have 1.5-2GB free just at first launch without anything open, and it then gets down to only several hundred MB's free with say Chrome, Outlook, iCal, and a few other small apps open.