Obviously the Auctions are cost effective for the winning bidder and the winning bidder alone. The actual money is made for Swoopo by the bids placed, this is why you'll find that the larger more expensive items are sold on 1p auctions and the less popular items have a fixed price to avoid disappointment.
Its definitely a good auction site for the individual, but be cautious with your bids and dont waste them.
Just a couple of weeks ago i won a Nnitendo DS Lite for £11.34 (I spent £7 on bids for that particular auction), I myself came off quite well but swoopo would have made their money back before i even won the auction.
Be aware and bid well and you cant lose :o)