I think the garage sale bargain can be distinguished. In that case, a human owner knowingly offers a cheap price and parts with the priceless item at that price. Here, on the other hand, I don't believe that any human at UA (aside from perhaps malicious employee(s)) intended to sell these tickets so cheaply. The tickets were sold by a machine, and humans discovered the pricing after the fact. It is not the same situation at all, IMHO.
(Note that I don't have a dog in this fight, either.)
I'm talking about granny selling what she thinks is a tchotchke and in actuality is a rare Hummel. So, a buyer knowing it is a rare Hummel buys it for $5. Granny would have never sold it for $5 if she knew she could sell it on eBay for $500. Is the buyer also morally bankrupt in this case? Or did the buyer just get a good deal?
Also, there are a profusion of auction sites. People buy products for pennies on the dollar. Same could be said for this deal. Ridiculous low price for a sought after commodity. Also, look at time share buying sites. Some condos going for $1. Also a ridiculously low price for what often goes for thousands of dollars.
Just because something is sold for way under what others may think of as a reasonable price, doesn't mean that the sale wasn't legitimate. Price to value ratio is not a test for legitimacy.