If you click through to where they discuss how they estimate it you can see that they make some assumptions so that it looks higher than it likely really is. On

If you click through to where they discuss how they estimate it you can see that they make some assumptions so that it looks higher than it likely really is. One of the reasons for this is because it is used as a source for articles and drives traffic. Each of the listed articles talk about how inefficient and wasteful it is, so the site does have a reason to make it look as inefficient as possible.