Re: the airplane proposal, I would worry that people are too panicked in an evacuation to think through the scenario rationally, and would still grab their stuff out of instinct, possibly even slowing down evacuation by trying to then re-stow it. It's also not a repeat game in that a single person is very unlikely to evacuate an airplane multiple times, so people wouldn't be able to learn from their mistake (unlike the examples in your post with children). It's a great idea for rational actors, but I don't think people are rational actors in an evacuation. It still might be worth experimenting with the idea though to see if it works.

there is no clearer or more convincing evidence [of fair market value] than being unable to sell assets to cover even 5% of the wealth you supposedly have

The rest of your comment stands, but liquidity can be very different than valuation. To give a couple examples:

• Private equity and private credit funds have restrictions on how much money can be redeemed per unit time, and can even temporarily suspend the ability to redeem from the fund if there's underlying liquidity issues. The inability to redeem does not mean the fair market value is $0, even if there's $0 of liquidity at the moment.
• Startups often have clauses preventing anyone from selling equity without approval from the board. Investors might still be investing at $x/share but share holders can't realize that value.