Thanks for all the input. Concensus seems to be 'write it yourself', which is the answer I was looking for. I just wanted to cover by bases as its a cost cutting question I've been asked by my boss.
Our site is a great ecommerce site, give the customer what they want, great pictures, great product info, great prices, fast service.. i could go on and on... So from a user perspective, we're on the money. But from an SEO perspective, it's thin and not informative. So basically we dont tell the user what the pages are about using words, becuse the massive amoutn of products and prices do the talking. but being thin on content is leaving us out on the woods unable to be found by the users.
So there we have it. I'll be getting started on writing 500 pages of content for 500 categories, 300 words a piece any minute now.