I hear this all the time, but does anyone really think that the market cap is what you can really get for an asset?

It's a metric, one as "untrue" as an average or median. It's not a contract, and you won't get that if you change the market, which selling and buying does.

I don't think that means we shouldn't use it as a metric to use to get information from for comparisons. And I don't think that it's bad journalism to say that the market cap dropped by $100B when it did, even if that doesn't equate to $100 billion being burned.