For a sport that's basically free, running sure is full of ways to spend money.
My shoes are about a year old, so I need new ones, according to the experts. I should also have a second pair for cross-training. I have a heart rate monitor. I recently bought a Halo headband with speakers instead of annoying earphones that fall out when I run. I have Skins for cold-weather running and recovery. A Belkin armband for my iPhone so I can listen to music and use RunKeeper. I just got a FuelBelt for carrying water & electrolyte drink when running long distances. A running vest for cold mornings.
It's ok. None of it is truly necessary, I'm spending money on a hobby the way I have spent it on hobbies in the past (I do wish I could make the time to get back into sewing and knitting!) It's just kind of funny.