Cracked rear lens

all,

I recently found this on my car.

https://dl.dropboxusercontent.com/u/12007759/PriusC_CrackedLens.jpg



The light is still working and the crack doesn't diminish or do anything to my light at all.

I called the closest Toyota Service shop and they quoted parts and labor at $257.25 + tax.

What should I do?

Also, what could have caused this? Looks like a it was shot by a bb gun. I don't remember hearing it crack while driving. So it must have been parked already and then something/someone hit it.