There are instructions for restoring your faded/yellowed headlights on a budget. All you need is some 1500 and 2500 sandpaper and clear spray paint. I found the sandpaper and some automotive clearcoat lying around at the TechShop in Menlo Park so I thought I'd give it a try and it turned out pretty nice. I'd imagine you could buy the materials for under $10 though if you don't have the stuff lying around.
If you're interested in TechShop, check out their website, http://www.techshop.ws
. TechShop is a membership-based workshop that provides members with access to tools and equipment, instruction, and a community of creative and supportive people so they can build the things they have always wanted to make.