Frontier AI models cost 5x more for a 4-month lead

A Mozilla-commissioned report reviewed by Ars Technica finds that paying for top frontier AI models delivers roughly a four-month capability lead over free open-weight alternatives, at about five times the cost. The report tracks how quickly open models have been closing the capability gap with proprietary frontier systems.

Why it matters: This puts hard numbers on the 'open vs. closed' debate, suggesting frontier labs' moat is shrinking to months rather than years — pressuring the economics behind massive compute spending by OpenAI, Anthropic, and Google even as some labs float slowing development. It's a data point worth tracking alongside broader questions about whether trillion-dollar AI infrastructure bets pay off.