Elon Musk first-principles thinking: For Tesla, analyzed spot costs of battery metals (cobalt, nickel, lithium) per gram/ounce and reasoned that battery technology would reach target cost—nothing would stop it; for SpaceX, went to Russia to buy expendable boosters, found them ridiculously ancient (50 years old) and expensive, convinced himself that fully reusable first stage could fire repeatedly; demonstrates domain-independent methodology: identify physical/fundamental constraints, work backward from desired outcome.