Hello John and welcome to the forum.
Prices vary depending on many factors. Here is a link to the ones for sale on the Net Registry website.
http://www.zr1netregistry.com/ZR1_sale.htm
These are typically well cared for and prices reflect that. Compare what those are selling for with the one you are interested in to get a better idea of it's value. Of course in the end make an offer that is reasonable and that you can afford.
