Very old whisky (30+ years) is always expensive. Part of this reflects high demand - whether or not that demand is justified - and part of it reflects the lengthy investment by the distillery. A cask racked in the warehouse for three decades is necessarily taking up the space that two 15 year whiskies could be using... or three 10 year whiskies, and so on.
This 32 year old Ardmore - my favorite distillery - is a Scotch Malt Whisky Society ("SMWS") release, matured in a second-fill sherry butt for what appears to be the entire maturation. I assume the sherry butt was relatively inactive, to allow for a 30+ year maturation without over-oaking the whisky or saturating it in sherry and losing the distillery character.
