OpenAI’s losses roughly doubled to around $540 million last year as it developed ChatGPT and hired key employees from Google, according to three people with knowledge of the startup’s financials. The previously unreported figure reflects the steep costs of training its machine-learning models during the period before it started selling access to the chatbot.

Even as revenue has picked up—reaching an annual pace of hundreds of millions of dollars just weeks after OpenAI launched a paid version of the chatbot in February—those costs are likely to keep rising as more customers use its artificial intelligence technology and the company trains future versions of the software. Reflecting that capital drain, CEO Sam Altman has privately suggested OpenAI may try to raise as much as $100 billion in the coming years to achieve its aim of developing artificial general intelligence that is advanced enough to improve its own capabilities, his associates said.