One of the most hilarious (or, hilariously illogical) attacks on expanding bicycle infrastructure that I've seen repeatedly pop up over the years is the idea that "bicycle infrastructure costs too much." It only takes a few moments to reflect and put such costs into perspective.
For one, bikes are clearly much smaller and lighter than cars or trucks. So, the space needed to accommodate bicyclists is obviously much smaller, and the repairs needed from deterioration are also smaller. Furthermore, as you attract more people to bicycling, that pulls people out of their cars, reducing the deterioration and eventual repair costs of the car lanes. Naturally, the benefits improve even further when we think about bridges.
Looking at San Francisco, in particular, the San Francisco Bicycle Coalition recently published an article on the cost of a mile of bike lane in San Francisco versus a mile of other forms of transportation. The difference was stark, but PeopleForBikes made the starkness much more evident by creating a chart of those numbers. Check it out (be prepared to scroll for a while):
Again, the stats, if you didn't notice them in the graph, are as follows:
1 mile of Bay Bridge eastern span:
1 year of the SFMTA budget:
1 mile of Central Subway:
1 mile of Doyle Drive:
1 mile of basic protected bikeway:
1 new traffic signal: $280,000
1 curb extension: $78,000
Percentage of MTA budget spent on biking: less than 1%
I think the implied discrepancy in spending versus use is one that deserves more attention. In San Francisco, despite receiving about 1% of transportation funds, bicycling accounts for 3.5% of trips. The percentage of transportation budgets that goes to bicycle infrastructure is almost always much lower than the percentage of people who bicycle. Seriously, anyone opposing bike infrastructure should never bring up costs.