As a whisky drinker, I was pretty happy with the offerings. Most of what's on board is included. Each bar venue will have a list of ultra premium options available for purchase. Well below typical bar prices. Yes, I sampled most of them...
Macallan 25, Yamazaki 18, Laphroaig 30, Elijah Craig 23. Those are all $1k+ bottles. The Macallan was the most expensive, at around $100 for a pour - it's usually 3x that in bars in my experience. Ultra premium pours measured from a shot glass - that's 1.25-1.5 oz?
Highland Park 18, Blanton's, JW Blue, etc. were available at much lower prices. Most of the premium options fell in the $13-$20 range on our recent cruise.
Free (included) stuff I remember off the top of my head: Macallan 12 (sometimes Quest), Highland Park 12, Woodford Reserve, Knob Creek 9, Basil Hayden's, etc.