There are allot of different vendors for Birkenstock on Amazon and, in my opinion, ya got to be careful that you are getting real leather instead of the Birkobuc fake leather.  I have leather Birks that are over ten years old and still going strong.

These are real, black leather Birks and I paid $77.00 for them.  Fast free shipping and a trouble free transaction.  Highly recommend Amazon and Birkenstock.