How much may I pay?

[Tinny]

Hi,
I've been collecting old wines for about a year now and now I'm able to buy a bottle of old Champagne. On the label I can read : Blason de France, Perrier-Jouet à Epernay. It dates from 1966.
The gentleman has 9 bottles of them.They are packed three in an original box and they are in very good, some in mint condition(they have been wrapped all the time!).
I'm considering to buy one of them.The asking price is € 515.00.
Is that a good price or is that too much?
Can anyone help me?
Thanks