Hmm. I dislike Ticketmaster and I am sympathetic to your sentiment, but the argument used here is flawed. Is it a live concert? If yes, does everyone has to have the same level of access to this entertainment/culture? If yes, there is appx. 7.8b people on earth now. Are they all guaranteed access to entertainment and culture?
The music is still accessible at libraries. Live entertainment is definitely "inessential":
lux·u·ry
an inessential, desirable item which is expensive or difficult to obtain.
plural noun: luxuries
"luxuries like raspberry vinegar and state-of-the-art CD players"
“Inessential” is subjective. There isn’t a thing in the world where you can’t find someone making the argument that it’s inessential because it’s not essential to them.
And using price a test of luxury in a discussion about monopolies is kind of circular; it leads to saying that anything a monopoly has successfully captured is necessarily a luxury.
That gets you to prescription eyeglasses being a luxury, because I don’t need them, people can just buy contacts, and a monopoly has driven the price to astronomical levels.