OpenAI has completed a deal to help employees sell shares in the company at a US$500 billion valuation, propelling the ChatGPT creator past Elon Musk’s SpaceX to become the world’s largest start-up. Current and former OpenAI employees sold about US$6.6 billion of stock to investors including Thrive Capital, SoftBank Group Corp, Dragoneer Investment Group, Abu Dhabi’s MGX and T Rowe Price, a person familiar with the transaction said. That boosted San Francisco-based OpenAI’s price tag well past...