I just came across an example of a road where the difference would probably be a factor of two.
The Shot: Contador's longest goodbye | VeloNews.com (Angliru, Stage 20, 2017 Vuelta a Espana)
This as gravel? The subject of this shot would have had to sit at a huge cost to his climbing abilities. (I know. I recently did a ride here west of Portland with those kinds of grades and gravel. I climb like that guy. well not as fast. It was brutal.)
Ben