Is it a lot in comparrison to the costs to the taxpayers for all the emergency crews responding to animal caused accidents over the lifetime of the crossing, not to mention dealing with carcasses of animals, etc?
How much of any single person's tax money went into it? How long until those few cents get paid off in terms of saved time and gas by not dealing with the traffic backup from those accidents? How much do those few cents amortize to your savings in reduced insurance since thats less potential accident you have to bet against... how much savings does that reduction confer on your expected direct costs in cas you had been in a the accident?
Does 15M still seem like a lot?
Maybe you think it could be built cheaper - how? Show your work.
All these things sure are an interesting conversation to have. Much more interesting than "hur dur, 15M is a big number" anyway.