In 2008, Twitter introduced the ability for advertisers to buy promoted trends, a way of taking over a portion of the homepage to drive traffic to a topic. At launch, it was a "mere" $80,000, a number that many experts thought was too high. In 2013, the number is officially $200,000. So much for the experts.
According to AllThingsD:
The promoted trend lets an advertiser insert its own message atop the “trends” list on Twitter.com home pages and on Twitter apps; Twitter sells a single message a day, per territory. Except when it doesn’t: Today, for instance, there’s no promoted trend on the site.
