Here is the other factor - the poor income from CD and generally physical releases sales. You know, composing process, hiring the studio and producer, costs of production, distribution and commercials. And all those thing just to sell some 300 - 500k albums worldwide. Sounds sad and lame, but this is reality of music biz of today. Who knows, my fingers are crossed for (at least) just another studio album.
Maiden are still comfortably selling over 500,000 units per album, and much of that is on the more lucrative vinyl format.
They also have reoccurring streams for any new album.
Senjutsu probably made more than Virtual X11 in terms of revenue.
And as others have said, there are also plenty of money to be made from related merchandise sales of the new album.
A new Maiden album may not make the band the millions that their classic albums did, but for sure it will still be a money maker.