This doesn't quite apply to your question--well, it does, but in a roundabout way.
I just read a wonderfully useful guideline that I think could be applied perfectly to either shopping or closet purging; actually, I misunderstood the headline, but I like my interpretation. The headline was "Will a $400 dress simplify my life?" And it suddenly came to me that that question would be tremendously useful for making purchasing decisions (for clothing, for kitchen items, for cable TV subscriptions, anything), because we all want life to be simpler--not necessarily more spare or spartan, but simpler.
I am very much not the kind of person who would ever consider buying a $400 dress, but I might consider, say, a $100 dress. No, that's a lie, because my lifestyle doesn't require dresses, so having a perfect little dress in my wardrobe wouldn't actually simplify my life. I would consider a $50 pair of jeans, though, because I have so many pairs of jeans that aren't quite right that when I want to look cute I have a hard time finding one I want to wear. But $50 is still a lot of money for jeans in my book, especially since I have so many imperfect pairs already, so that's where the question "will X simplify my life?" comes in. Are the jeans (or t-shirt, or sweater, or whatever you're trying to decide on) going to make life simpler by being a perfect, effortless, flattering go-to item, or are you only considering the purchase because it's a good deal and it will just be in the way once you get it home. And are the pants you're considering giving away simplifying your life at the moment, because you need something basic to wear until you find the perfect pair?
I only stumbled across the headline and had this epiphany a few minutes ago, so I don't know yet how well it will work when I shop or when I weed out my closet, but I thought I'd share it here because I think a lot of us with stuffed closets tend to focus on the joy of bargains when shopping or on the fact that we haven't gotten our money's worth out of an item yet when we're purging. A minimal closet really does make life easier (or so I hear--I've never had one). "Will buying it or keeping it simplify my life?" is going to be my new question the next time I shop or purge.