If you want view ticket pricing as a pure economics problem (it is not), consider that live shows are also a way to build up and expand a fanbase. If only a handful of rich people (or people who bought tickets the second they went on sale) are at your show, you are not expanding your audience. Since streaming has decimated most artists' income from record sales, it makes sense to try and build a large fanbase who will regularly come to shows as well as buy merchandise. Tours often have exclusive merchandise than fans will want to buy, so all the more reason to attract more people.

As a side note, this notion that a phenomenon being the result of market forces means it is fair and has no issues seems to be a blinkered view of the world. Surely enjoying high quality art should be possible for a broad section of society?