Maybe the NVCA statistics are somewhat bogus, but there is a pretty compelling way to answer the question empirically: how many tech companies have made it as far as an IPO without taking money from VC funds?
Maybe the world is changing. Maybe now that it's cheaper to start startups, some will start to make it all the way to IPOs without VC funding. Obviously I would love it if a company we funded could make it to an IPO without any further dilution. But that seems like insanely wishful thinking.
How about some combination of Revenue + Profitability?
Revenue alone doesn't help, I think Facebook crossed $300 MM but was not profitable at that point in time.
Current IPO's target revenue in the range of $50 MM (I think), pre-bubble IPO's required 4 straight quarters of revenue growth (something like that), this is a moving dynamic.
For what it's worth, my understanding is that the target these days (especially thanks to the costs of Sarbanes-Oxley compliance) is closer to $100 MM in revenue to even think about an IPO.
The issue with IPOs as the marker of "success" is that public market investors are much more hostile to companies without the VC stamp of approval - they're relying on the implicit due diligence of the VC firms to make sure that there are no issues with the technology, the patent landscape, and other various hangups. (This applies much more to health care companies, where my VC experience was, but the mentality is the same as the public market investors are the same regardless of industry.)
Having the "stamp of approval" is a bare minimum requirement to go public; you can't find enough buyers of the securities without it. The pricing, as you say, is affected by the financials and (I dispute this, but hey, it's not germane) the underwriters.
Maybe the world is changing. Maybe now that it's cheaper to start startups, some will start to make it all the way to IPOs without VC funding. Obviously I would love it if a company we funded could make it to an IPO without any further dilution. But that seems like insanely wishful thinking.