I make my own. I have tried a few commercial rubs but did not think they were any better (or not as good) as what I make at home.
Also, when I look at rubs in the store and then look at the prices ...
I know some say that making your own is not really any cheaper then buying a ready-made. Maybe it is perception, but it doesn't seem that way to me.
Besides, I always have what I need to make a rub at home.
Like others have said, I usually just throw things together ... don't measure most of the time. Even though it means that I don't get the exact same rub twice, that is the wonder of Q