I take your point, but I think a lot of people are willing to put $15 into snagging their favourite username. That's why so much effort has to go in to policing username trading, after all. Also, there are still quite a few people who have a pretty good idea what DW is, because many of their friends are on it. Being able to get their username with minimum hassle (even if it costs money) may make the difference to some, I think.