Ultimately, pursuit of perfect efficiency results in crystalline systems which are fragile. Slack is the ur-antifragility. (efficiency pursued for itself is AN enemy)
That's because the risk of fragility is typically not priced in. If risks werent treated as an externality this failure mode would be taken care of. Of course some unanticipated failure modes would always come and surprise us. I would be one happy person if the failures we see around us were all of this 'inconceivable' variety. Very few are, except when one buries one head in the sand and refuses to consider the fair…
For example, the financial entity that makes tons of money speculating in a worthless asset, then goes belly up when its worthlessness is exposed (I won't name the asset(s) to avoid a flame war).
You can't "price that in." You just avoid it.