Kardashians, Charlie Sheen Among Stars Earning Up to $71 Per Character for Sponsored Tweets

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Brands say the return on $10,000 tweets is worth the investment -- when the paring is right.

Brands have been paying for influential Twitter users to write about their products since Justin Bieber was just barely over $1 million followers.

And these days a single sponsored tweet can run $10,000 or more. But what's the return?

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The AP reports that companies remain committed to paying for actors, musicians and reality stars like the Kim and Khloe Kardashian tweet about their products, pointing to specific examples where large Twitter followings equaled high click-through rates.

When Charlie Sheen was in the midst of he very public exodus from Two and a Half Men, the actor joined Twitter, almost instantly reaching 1 million followers. Soon after, Internships.com paid Sheen to link to its site.

"I'm looking to hire a #winning INTERN with #TigerBlood," he wrote in March. The website claims 95,000 clicks came from the first tweet after just an hour.

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CampusLIVE, a website that connects advertisers with college students, paid Lindsay Lohan $3,500 for tweet about the company to her 2.6 million followers.

And though CampusLIVE marketing vice president Dan Smith says it prompted 4,500 clicks, he also says he doubts he'll use Lohan again, saying the one tweet tapped her fan base.

Twitter's role in this process is limited, as it generally allows paid tweets, but a company spokesperson encourages transparency, noting it makes a "more powerful connection" to the audience.

The Federal Trade Commission wants that transparency to be a trending topic of its own, suggesting endorsers cap off tweets with a #ad or #spon to spell things out.