I got a pair of Shimano SPD shoes with carbon soles on Craigslist for $45 about a year ago. They were used, but still worked pretty well. The "hot spots" I used to get on my foot, near the contact area with the pedal, went away instantly.
I just got a pair of Giro carbon soled mountain (SPD) shoes at REI's sale. Haven't put the cleats in them yet ... I had a root canal recently and it's still bothering me a lot, so I don't need an excuse to get on the bike and make it worse!
EDIT: I don't wear bike shorts, either, or other bike specific clothing. But the shoes and pedals make a huge difference!