Well, the fare rules that you posted are very clear: cancelling is not allowed, which means that if you cancel you simply lose everything. They would not give you a voucher or anything else, that is why it is non-refundable while other (higher) fares are.

However, it is changeable against a fee of $250 plus any difference in fare. This means that if you are sure of your new dates, you could rebook against that fee. Of course, if you have no idea about what new dates you would want to rebook for you could simply lose even more money. Also you can only rebook within 330 days so if, say, you want to travel after March 2014 or so it wouldn't work.

Of course, if the reason for your cancellation is a major medical reason or equivalent and you have travel insurance, the said insurance would kick in.