I think ethbro is saying that focusing on absolutely secure systems would drive up costs, not that if we make them more expensive we'll somehow get more security just because they're more expensive.
For example, the parent article, the one this comment is ostensibly in response to, has nothing to do with operating system security.
A better example is maybe instead of Google spending $xxx,000 to develop the system that was found insecure they should have spent $x,000,000 so they had more resources devoted to the security aspects.
Perhaps this is too high for this system to exist; well maybe that system just shouldn't exist if it can't be secured properly with the budget for it.