If I had to guess I'd would say that the people who bought the site had offered 480k but you didn't want to say that you had a solid offer for a certain amount. Speculating that you told them you would sell to them at that price if a better offer didn't come in. This seems to dovetail with the somewhat cavalier attitude of previous posts and 37signals principals HN comments.

"despite the HN peanut gallery's perception of the world, there is actually a market for profitable businesses."

I've bought and sold several businesses both as the business owner and as a go between (collecting a commission for the sale of a business).