The trick to getting away with being corrupt is to as corrupt as you can without your marks/customers/voters/whatever revolting¹. Switching ticket sales to an auction format would likely add enough friction that many people² wouldn't bother, bringing the price back down, or would make a very public noise about how unfair it feels.

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[1] or authorities taking action, but that usually comes after the marks/customers/voters/whatever speaking up loud enough, unless by “taking action” you mean “taking a piece of the action” by way of being corruptible themselves.

[2] from those who do, or might in future, play along with the current race-to-buy-at-fixed-teered-rates system.