Sadly, in the 11 years since the article was published, the Battlefield Earth official movie website has gone dark. This little section of the book's website seems to be all that's left:
But it uses flash
https://www.boxofficemojo.com/title/tt0185183 describes the success of the movie: budget $73M, worldwide box-office < $30M
Okay, it's closer to 175% of what the budget was. It was around 42M. And it was the North American box-office that was just under 30M. I don't know if they released elsewhere.
All Releases DOMESTIC (72.2%) $21,471,685 INTERNATIONAL (27.8%) $8,253,978 WORLDWIDE $29,725,663
"Domestic" refers to gross box-office revenue from North America (U.S., Canada, and Puerto Rico), unless otherwise noted. "International" covers the rest of the world.
I saw a different source that quoted the numbers differently. Either way, it was a movie that did poorly commercially. Although it probably made back its production costs. See the other part about the lawsuits claiming it really cost a lot less to make. Probably because Travolta "invested" millions to pay his own salary.