Condition, presence of attaching hardware and rear window glass(not plastic) are most important. Next is location relative to real buyer.
Freight can be a big expense for the buyer.
If everything is correct and the the top just needs refurbished, $500 could be a good price to get. Price can go up and down from that point.
It is important to remember that only factory tops will command a good price. There are many aftermarket tops for Bugeyes that are of little or no value.