Fourth power law - Wikipedia
The Reality is that, although measurable, the Actual wear on the roads due to weight isn't as great as people think it is.
The difference in your example is ~16 to 1 or 16x the wear of the 3500lbs vehicle.
This is insignificant when compared to the Wear caused by medium and large trucks. Which are over 10,000 times that of a 4,000 lbs vehicle