The biggest cost of PKI
PKI is notoriously expensive. The US government alone has spent over $1 billion on the technology and doesn't really seem to have much to show for their investment.
But there are actually even bigger costs from PKI.
Remember the dot-com era?
Baltimore Technologies, a PKI vendor who actually had a fairly good product, at least relative to other PKI offerings, once had a market capitalization of roughly $13 billion. Their revenue never justified this valuation, of course. It actually never even came close. Instead, this was just based on the assumption that PKI was going to be an important enabler of the future Internet.
That never happened, and essentially all of that $13 billion disappeared in a very short time.
That's one of the biggest costs of PKI.
And I'm sure that you could even find several billion of lost value from other companies that was directly due to PKI not working out. And that's the sort of cost that even seems to make the $1 billion that the US government has spent seem relatively small.