I'm on Mavericks 10.9.2, 24GB's RAM, and my usage constantly teters on 23.95 GB in use very frequently.
From what I can tell, the largest running process is 'kernel_task', and even then it's less than 2GB.
The only way to reduce this amount used is using the sudo purge command in terminal.
Is it ok to do this frequently to speed the system back up?
There isn't a good reason to run it (as detailed here). Inactive memory won't slow things down (I haven't stress-tested it myself, but it makes sense to me). Inactive memory is second only to free memory with malloc, etc.
Inactive memory is just used for keeping things around so it won't have to load them from disk again. If you open, say, Terminal for the first time in a while (or after a reboot), you'll notice it takes a couple seconds to get a prompt. Quit and reopen it (or just make a new shell window) and it's almost instantaneous.
That said, running sudo purge all the time won't break anything. I would recommend setting up an alias/function in your .bash_profile as you don't want to mistype anything prefixed with sudo. (The results could be disastrous, and I mean it).
But with 24 GB of memory, there is no reason to run it.
