If a road is left to deteriorate, rebuilding the road costs between 7 and 10x the cost of maintaining it. It's like letting the paint peel on your house before deciding to repaint. At that point you have to scrape off all the old paint first.
We let our roads get into such a bad condition that many need to be totally rebuilt. Doing that is very expensive. Making a guess here, but I'll say about $500,000 to $1,000,000  a mile. How many miles of streets does Eugene have? 
I am amazed we are actually catching up. Once ahead of the problem, the cost of maintenance would be a fraction of what it is today.