I work for William Grants, who make Glenfiddich, and even a bottle of 40 year old will retail at over £1,800. We dont make an 80 year old Glenfiddich but if we did, the cost would be very high! If you are willing to spend the cash, then I would recommend contacting someone at The Whisky Shop, link below.
http://www.whiskyshop.com/
edit: Just looked on there and the longest aged whisky is 59 years, a snip at just £15,600!