Great thoughts, Jason. Your point about the change in valuations is more than an observations, though. Implicitly, it suggests that valuations are less a function of the companies themselves and more a consequence of exogenous macroeconomic and industry specific factors.
This is sort of a scary realization to me, because it means that "crushing it" isn't a strategy to preserving valuation. Perhaps the Dropboxes of the world will always be able to name their price, but for the rest of us valuations will come tumbling down if the outlook turns negative on the startup asset class or economic activity broadly.
Startups taking a more conservative approach to valuation and amount of capital to raise may be much better positioned to raise subsequent rounds of financing when the market, as all markets do, regresses to the mean.