Code the falls between between "I need an experienced team member to see the issue" and "A few static analysis tools would no doubt have seen it" must be vanishingly small.

For specific areas, I can see myself paying for external code review. For example some open source library authors sell it as a service, so they can review the specific parts of the code where the library is used. Rob Menschings FireGiant is one such example.

Security reviews (Audits) I can also see a good use for. The current practice here is already to have external non-domain-experts review the code. So making that simpler or more frequent is a net win. The reviews I see little use for would be normal feature code, (pull request reviews) which need a lot of context and domain knowledge to even begin to review.

Not audits, or reviews of specific areas or aspects of the code.