I bought some replacement rear spokes last year. They were $35.00 each.

However, I think the odds of you breaking one is pretty slim. Ive ridden the crap out of mine and theyve never even gone out of true. I weigh about 240 and Im hard on wheels.

The front spokes might be a little cheaper OR all of them could be cheaper since Campy is handling all the Fulcrum stuff now instead of it going through a 3rd party like it used to.