The San Francisco start-up’s valuation could triple in less than six months. : OpenAI is in talks to complete a deal that would value the company at $80 billion or more, nearly triple its valuation less than six months ago, according to a person with knowledge of the discussions. The company would sell existing shares in a so-called tender offer led by the venture firm Thrive Capital that would make OpenAI the most valuable start-up in San Francisco, that person said. It was reported earlier by The Information. Nearly a year after OpenAI sparked an A.I.