The assumed time requirement simply establishes an infinite present value lower bound on the cost in money. This becomes clear once you admit the possibility of

The assumed time requirement simply establishes an infinite present value lower bound on the cost in money. This becomes clear once you admit the possibility of an incorrect current understanding of the mathematics. (Admitting the possibility of an incorrect current understanding of the mathematics is, like, a major reason to go with the enormous overkill on key sizes we do.)