How much is a Twitter follower worth? Is there an industry average value per follower?

[Janie]

I'm wondering how companies value their Twitter followers, assuming that they are real Twitter followers, not fake or inactive ones. Is there an average value per Twitter follower that has been proven/supported by reliable sources in the industry?

Thank you for any suggestions.

[956]

For some politicians a higher number of followers might mean more political influence
For a commercial brand, more followers might mean more sales
Some use twitter for advertising: a higher number of followers meand better penetration and may chage more for ads.
Celebrities use it communicate "directy" with fans
You can fill the rest.
There is a site which gives a value to each twitter user according to number of followers. This might have some comercial value. There is a site which determines the number of "phantoom" followers, users who just follow but don't ever tweet!

Now, for any common people like you and me, the number of follewers has no real value. So all those fighting for more followers do it just to "show of"