B grade chipped or broken solar cells work just as well as whole ones. You may loose a few watts overall, but they work and they are cheap.

I got 600 watts worth of broken cells for $50 online in an auction. They are all half cells, but work fine. Just tape them together and make your solar panels. My 65 watt panel shown here cost $14.95 for the cells.

The plexiglas for the cover is the most expensive part of the solar panels, at about $22 for a 2x4 sheet.

http://www.thediyworld.com/DIY-Solar-Panels-And-Solar-Power.php

Make your own cheap solar panels.