I think that there is an argument to be made that charging someone money for not taking a flight is unconscionable, since the airline suffers no damages by you not taking a flight. Whether the penalty for not appearing for your flight is $5 million or $500 does not change this fact.
Until a court decides this one way or the other, there is no way to be sure.
However, it is abundantly clear that the arguments that "it's in the CoC and therefore it's enforceable" are incorrect. The only correct answer here is that it's undecided, and we will know for sure if and when a court rules on it.