The moat
Insurance float plus a reputation that lets Berkshire buy businesses and securities on terms others do not get. Diversified cash generation. Culture as an intangible asset — now the succession question.
Pain, risk, or retraining required to leave.
The product gets better as more people use it.
Patents, data, licenses, process knowledge, regulation.
Fixed costs spread over a volume rivals cannot match.
Structural ability to be the low-cost producer.
Pricing power from trust, habit, or identity.