SAN FRANCISCO The valuation of ChatGPT developer OpenAI soared to a chart-topping $500 billion in a deal for employees to sell a limited number of shares, financial media reported Thursday. If confirmed, OpenAI workers' sale of a reported $6.6 billion in shares to investors would make the company the world's most valuable startup, overtaking Elon Musk's rocket company SpaceX -- valued at around $400 billion, according to Bloomberg. A gaggle of investors snapping up the shares included Japanese