I am not sure that it is price which will dictate useg of the vaccines. It is effectiveness. I would pay $100 and more, just to have some relief.
Awards are uncontrolled, more like social help that GOV is doing right thing.
IMO, IF challenge study generate +80% infection rate, effective vaccine should reduce that to <25%. Which is 70% relative benefit rate improvement.
50% (and probably it may come that 40%) improvement looks a loot, but actually it is not.