By far the vast majority of my cables and subsequent upgrade of said cable has all been used from either right here or eBay.
As already stated it is hard to lose more than a few dollars, you dont like the cables then you just put them back up for sale.
Another BIG advantage of buying used is that they are usually very well burned in and what you hear right away is just about what you are going to get, nothing worse than trying to put 150 to 200 hours on new cables!
Browse a few threads here, check out the Cable Company by all means, gives you an idea of new price then you know what to expect at used street level price
Good luck!