The total world GDP is around 80 trillion. A 2.5 trillion dollar problem is about 3% of total GDP. That is an astronomical amount of rust!
In the context of a thread about the precision of quantitative language, I feel obligated to raise an eyebrow (and type a comment about the raising of said eyebrow) at your use of "astronomical".
The number of stars in the Milky Way is supposedly about 250 billion, so anything in the trillions is well qualified to be considered an astronomical number.
Technically, it could be 2.5T because they never say annually. So may be they are talking about 100 years :|. That said, the QZ title is really misleading and click-baity. They have a simulated environment test and yet to tested for real world conditions.