I think the point you're wanting/trying to make is that private market valuations are ridiculously high. But that's not YC's fault. It should enjoy this while it lasts, and hope that as many of its investments as possible get to liquidity before the music stops.

A more interesting observation is that two companies account for over half of the $65 billion. Airbnb's most recent valuation was reportedly $25 billion, and Dropbox's was reportedly $10 billion. These companies are not likely to go away overnight a la Homejoy, but their valuations are going to be hard to sustain. Dropbox in particular would be a very tough sell to the public markets at its private market valuation given its comp[1].

Making analysis even more difficult is that today's big money, late-stage deals have lots of strings attached, so these valuations are hard to assess without knowing all of the details.

Final comment: despite the constant suggestions to the contrary, YC's portfolio appears to live in the very same power law reality as most early-stage investment portfolios in Silicon Valley.

[1] https://www.cbinsights.com/blog/dropbox-valuation-bubble/