Advertisers thinking of advertising on Facebook's log out page would need to take out a huge chunk of their revenue to get noticed by millions on the log out page.
The log out placement is rumored to cost $160000 per day in the United States. This is only available to advertisers who spend $550000 per day or more on News Feed ads.
The high prices will actually narrow down the potential buyers to big company brands who spend highly on advertisements. The $700000 commitment is just the same cost as for a single day homepage ad on Yahoo or YouTube.
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