I was just at a sport shoes store and they did some gait analysis on me in order to decide what kind of shoes I need. They figured out that I roll my feet in a little bit when I run, which I could have already told them. They figured it out by filming me running and showing me where my heel strike was. I figured it out by looking at where on my shoes wears down the fastest.
It's good to get slightly more expensive running shoes if you can, but if you can't, you should still try to figure out what kind of gait you have and get appropriate shoes. For example, since I roll my feet, I need stable shoes, with a firm sole, so I always try to bend the shoe slightly from side to side before I buy it to see how stiff the sole is.