Public equity markets show structural constraints absorbing frontier AI and space firm valuations exceeding $150B each, per private round data. OpenAI reached $157B valuation in 2024 tender offers documented in The Economist archive, while SpaceX hit $210B in late-2024 secondary sales. Anthropic followed at $40B post-2024 funding. Historical IPO liquidity thresholds from 1999-2000 and 2020-2021 cohorts indicate dilution risks above 0.5% of total market cap per listing. SEC Form D filings and Fidelity SpaceX valuation marks reveal revenue multiples at 40-60x versus public aerospace peers at 2-4x. Primary capital flow data from Treasury and exchange reports confirm private rounds bypassed public absorption channels at unprecedented scale. Patterns in 2021 tech listings demonstrate corrections when private hype valuations met actual order-book depth.