The 1bn is only the out-of-pocket cost for development and doesn't factor in for instance opportunity cost. If we include everything required to develop a vaccine, I'd imagine we're looking at something north of 2.5bn

There's so many ways to calculate the cost, that I think it's more important to be aware of the assumptions made for the estimate, than the number itself (which I also failed to do in my original answer)

I think people underestimate the cost of drug development, because the numbers are so big, that it doesn't seem realistic for companies to survive