The author regrets missing early investment opportunities in OpenAI and Anthropic, highlighting their rapid valuation growth. OpenAI's valuation is projected to increase from $86 billion in March 2024 to potentially $300-500 billion by September 2025, while Anthropic is expected to jump from $18 billion to $183 billion in the same timeframe. This suggests significant upside potential in leading AI companies, though direct investment in these private entities is generally unavailable to retail investors.