From the same blog here is a good article about the sales of Michael and others:
http://www.hitsville.org/2009/07/12...8212;jackson-the-beatles-pink-floyd-and-more/
I think these figures are just about right. Especially because they also mention the Beatles and Elvis didn't sell as much as claimed either:
About the full record sales of MJ they say: "That’s around 80 million more than Elvis Presley, 40 million under the Beatles
***."
I think that seems about a good estimation.
They estimate Thriller's sales at about 63 million, which makes it still by far the biggest selling album of all times (second is Pink Floyd's Dark Side of the Moon with 42 million).