Here is an example frequently used in introductory microeconomics courses: https://en.m.wikipedia.org/wiki/The_Market_for_Lemons
In this example, information symmetry would be better for the majority of market participants, and no worse for the remainder.
It seems that at best there will be a small amount of information asymmetry and that should the randomness of bag prices get too bad, someone will be incentivized by the market to publish bag prices.
At worst, it will lead to something like GasBuddy where consumers input what flight they took and how much the bag cost.
The idea that the market for airlines will completely break down because there is no regulation on bag fees seems a little... far fetched.
My comment was a direct response to the parent comment, which claimed information symmetry isn't cited as a requirement for functioning markets.
That particular statement is untrue, so I replied.
A lot of the value in things like the stock market is to disseminate the various information asymmetries in the form of price.
There's a reason guys like Paul Krugman write books on economics rather than trade the market.
EDIT: Don't take my word for it. Look at the SEC web site's description of their purpose. Excerpt (emphasis mine): "To achieve this, the SEC requires public companies to disclose meaningful financial and other information to the public. This provides a common pool of knowledge for all investors to use to judge for themselves whether to buy, sell, or hold a particular security. Only through the steady flow of timely, comprehensive, and accurate information can people make sound investment decisions."