I vehemently disagree with this.
A false negative means either work isn't getting done or current people are overworked. This is costing your business. If it isn't, why are you hiring in the first place?
As for the cost of false positives being "huge", how? All you have stated is that a bad hire brings down the net productivity of a team. How much is very relevant and something you can get a rough feel for. If I hire someone who has a slight net negative impact on team productivity, and they show no signs of improving, I fire them and move on. Is it a worse outcome than not hiring them or anyone else for that period of time? Yes. Is it a huge impact? Not at all.
You can come up with a hypothetical worst-case, company-destroying false positive, but that would be comparing apples to oranges based on your position concerning false negatives. The worst-case false negative situation is also company-destroying.
You don't quantify the impact of false positives the same way you do the false negatives. A false negative simply means you take more time to look for a candidate. A false positive's impact is so huge that you can't come up with numbers large enough for false negatives to outweigh it.
To make a broader point, not everything can be tracked and measured. Things that can be tracked and measured often can't be compared to each other usefully.