HID lamps are expensive, yes.However, they also last much longer than traditional halogen lamps, and provide vastly superior illumination.
Unfortunately you'll almost certainly end up spending more to convert to halogen than you will buying a replacement HID lamp.
Shop around for D2R lamps and see if you can find a better deal. I'm sure you can find them for under $100 easily on ebay.
Here's another link to the replacement lamp listing above if that one doesn't work. You'll just need to tell it which car you need lamps for.
http://www.sylvania.com/Consum...Guide/