I don't think many (if any) were chosen. Most paid $500 to get it early. Anyone who wanted to get it early was able to. Most people didn't get it early because they knew that they were able to get it for a lot less (and fully functioning) if they waited for it to be publicly released. 😉
Well, there are some people who pay the $500 only to get Tiger early. However, the idea is that you pay $500 because you need Tiger early, so that you can develop software for Tiger.