Bidwoman.com works in an easy way: the winner is the one who makes the lowest bid,that is the unique.what does it mean? The Lowest unique means that she is the only one who proposed that bid.

here's an image:so for example 2 people bid one euro cent, 1 person bids 3 euro cents, 3 people bid 5 euro cents and 1 person bid 7 euro cents; the winner is the person who has bidded 3 euro cents because her bid was the only and the lowest one.