This initially appeared on Postlib.com.
We usually underestimate the time and cost required to bring a predicted innovation or technology about (this is probably equally true of our personal lives as well as on grand scale).
But when that innovation or technology does arrive, we usually find ourselves having underestimated its impact, power, or effect.
We usually underestimate both:
The time and cost required to bring a technology or innovation about.
The eventual impact, effect, and manifestation of that technology or innovation when it's finally achieved.