Is it more expensive than the potential downside if you run into one of these bugs? Sure, living dangerously allows you to avoid paying any up-front costs (e.g., the price of this tool), but on the other hand, without a tool like this it's hard to even tell what the probability of failure is or how much it'll cost you if something does fail.

Viva64 is not cheap, but it looks like an extremely solid tool; I'd imagine that for anyone with a reasonably large C/C++ codebase, it'd quickly pay for itself by offsetting time developers would otherwise spend troubleshooting, tracking down, and fixing bugs.