Why is the sales and revenue estimations different from others like Jungle Scout, Viral Launch

Why is the sales and revenue estimations different from others like Jungle Scout, Viral Launch?

Each tool comes up with its own interpretation of sales and revenue estimations. Because Amazon does not disclose the sales data for the products in its catalog it is impossible for each tool to give you exactly the same numbers.  AZInsight Sales and Revenue estimations are powered by real live data provided by Keepa.com and ScoutOracle. 

Comparing AZInsight sales estimations with the Jungle Scout numbers? Beware that Jungle Scout returns extremely inaccurate sales estimations numbers on their FREE sales estimation site compared to their paid extension.