Also, this is not out of the blue. We lost interest in considering all sorts of complicated deals a while back. So we told everyone that the price was $480K and that the deadline for closing a deal was July 1st: http://37signals.com/svn/posts/3172-sortfolio-going-once-goi...
So there was really no "bidding" after that point. It was quite simple: Give us $480K and the site is yours. The new buyer's did just that. End of story.