Let me know if I’ve screwed up this math somehow. Portland’s population is 593,820. Portland’s bike share is 5.44%. This means 32,304 people use the bike infrastructure (bip = bike people) and 561,516 people use the freeway (fwp = freeway people).
The city spends about $65,000,000 per mile on the freeway (fwm = freeway mile). This does not necessarily include the planning that goes into building a freeway and definitely does not include the maintenance of those freeways. By my Google Maps search, about 63.5 miles surround the city (for which I don’t know how much Portland is actually responsible).
So based on my information it costs about $4,127,500,000 just to build the whole freeway system.
$65,000,000 / 63.5 fwm / 561,516fwp = $1.82 per fwp.
$433,333.33 / 150 bim / 32,304 bip = $0.09 per bip.
Even if you perceive bike infrastructure as being something that “most people won’t use” and even if my freeway calculations are vastly wrong it would still take a lot of fudging to get that number anywhere close to a nominal difference. It’s hard to argue against: there is tremendous value in bicycle infrastructure.