For me it differs, like one time I'll spend like 300 (I'm from Oz so it's in AUS Dollars) and other times I'll buy an eyeshadow here and there.
I'd say approximately I spend about the same as you. But in the last few weeks I've drawn myself up a budget and have put about $20 a week away for make-up (and an extra $15 a week for make-up for my course so it's not too bad). I think that I'm at the point where I have so much that I don't really need any more (except for foundations when they run out etc.), I just want more XD.
So far it's going well. At the start it was hard (it still is) but it gets easier and is nice to know where all my money's going instead of going on big spend-ups all the time haha!