If you're looking for an absolute original German scope, with all the birds and numbering to go along with it, they're extremely pricey.
On the other hand, if you're just looking to do a buildup sniper, you can quite often find original era scopes for a few hundred dollars. Remembering that the Germans used commercial scopes and, quite often, the only difference between a commercial scope and a military scope is the WaffenAmpts they've stamped on them. If you want to be really picky, do a bit of research and find out which maker was prevalent with which era rifle and which type of mounting system (Hensoldt or Kahles scope on a Mauser production rifle for an early war short rail mount, etc).