We did it for our son. Why not, you never know what they will be able to do with it in the future. At least you know you did everything you could. If you got the extra cash, do it, but don't get yourself into financial trouble because of it.
Make sure they harvest it RIGHT after the birth. Our Dr. forgot about it, and didn't do it until half an our after the birth, which resulted in not an optimal sample. Good luck with everything.