Traffic value, or acquisition value, is a metric that represents the estimated cost that would be needed to acquire that same amount of traffic from pay-per-click (PPC) advertising on Google. 

Traffic value is calculated by multiplying the cost-per click for the keyword by the estimated traffic (rank position CTR x search volume) for the keyword, relative to the date range selected.

Traffic value can be seen in features like SEO Forecasting and Research Grid.