If I calculated correctly (by multiplying someone's per share book value estimate by a published number of shares), the Sick Bird had a "book value" of about $6 billion based on its last financial statements before the buyout.
Book value is, more or less, the total value of tangible assets, so it should represent roughly the value of a company if it is broken up in bankruptcy. It's a complicated thing to calculate.
Fidelity owns a small stake in Twitter and is required to periodically estimate the value of its stake as part of its obligations as a public corporation. Dividing its valuation of its stake by the percentage of the whole that its stake represents, the whole is worth about $15 billion.
1/3
https://www.reuters.com/technology/fidelity-marks-down-value-twitter-stake-again-2023-05-30/