Look on the skimonline.com forums, lots of used boards for sale. I've picked up a few from people on there back when I used to skim. Check craigslist too.
I have a large Harvest Skimboard ill sell for 250. I paid 500 2 summers ago. its a great board. Carbon fiber also. Email me for details @ jdreynolds44@yahoo.com
id also sell my brand new exile carbon fiber but i would want at least 350 for that because its Brand new and i paid 475