I think so many has made that much amount since most of the campaigns are paying upto 0.03BTC per week. I haven't made anything from Signature campaigns because of my rank level (Junior).
Try participating in signature campaigns and see how they are paying for every level.
Read this thread
https://bitcointalk.org/index.php?topic=615953.0Yes! Me and everyone love to participate in campaigns. Because we can earn a fair amount of money from those campaigns. Every time the campaign opens I work hard to invest my time and energy in them. But in exchange for each campaign, I get paid well.