> The calculation is "what could that engineer be doing instead and what is that worth vs fixing this issue?"

I don't agree with this, because it pre-supposes that there's a limited number of engineers available. The question isn't "shall I pull engineer X off project Y so that he can fix security bugs?", it's "shall I hire an additional engineer to fix security bugs?". The comment above mine suggests the answer to that question is "no, because it's too expensive to do that compared to just paying to clean up security breaches after they happen", which is what I was questioning in my first comment.