These are the average prices I've seen Z50R parts sell for on Ebay lately:
(These are prices for parts in very good or excellent condition only..)
Seat $50
Bars $30
Wheels $50 each^
Shrouds $45^
Tank $70
Front Fender $20
Number Plate $15
Don't spend more than $200 on it. Less if not running..
Have fun wit' it!