Am I paying my share?

The Mary Peters fallout raises an issue that always seems to be aggravating the cycler/driver divide. Do cyclists pay their fair share for the facilities they use? It seems like as soon as anyone asks the question, it changes into "Should they pay their fair share?" and pretty quickly each side is lobbing in complications until the question is unanswerable. I, for one, would really like an answer to the actual question. As a cycler, just what is the difference between what I pay into the transportation system and the costs that I impose on it?

Now, I concede that there are external benefits to utility cycling like freeing up road and parking spaces for someone else. And, at least a particle or two of air is that much cleaner given the exhaust I would have released. But, suppose I choose to give all of those external benefits as gifts to the world, what about the more basic question?

Does it boil down to the amount of road user fees (which I don't pay, directly) that is spent on the bicycle facilities that I do use, times my share of overall use of the facility? I suppose one should include some small cost for using any street, since I do take up a small piece of moving real estate. So, say the annualized cost of bicycle transportation in Portland is $1 million (PDOT estimate here is $3.5 million over 5 years for capital projects), at most about half of that comes from road user fees (here), and my share of annual Portland bicycle miles is 1/15,000th (based on 3% of Portland trips made by bike and 500,000 residents). That would put my share of the unpaid costs at about $33 per year.

Hmmm, 14 cents per round trip commute. I think I could handle that, if push came to shove...