Probably 8 or 9 years ago there was a mistake on the Air Canada Flight Pass website. It was advertising a 10 leg, business class flight pass between Western Canada and Western US for $800. This would mean 5x return trips between say LA and Vancouver in business class for $800 total. It was obviously a mistake fare but many people bought a pass or two. Air Canada cancelled all the passes and it eventually went to class action lawsuit where each person received $450/pass in Air Canada credits.
Part of the argument was that Air Canada had pretty clear disclaimers that "Any advertised price will be honoured and cannot be changed or cancelled". I still have the screenshots of their pages somewhere.