And the cost for that scenario right now is the same as the flu.
If we DON'T overrun the healthcare system, the cost is not really measureable numerically. (Very measureable for each family affected, but that's true of every single tragedy).
We (And everyone else) runs our healthcare system at 80-95% of capacity. If not we couldn't afford to have a healthcare system at all. It doesn't take much to overwhelm a system that is already running at capacity. The answer is either to double the cost of health care during healthy times, or recognize that small focused health care impacts will ALWAYS overwhelm us.