That's only true if Boeing was the only manufacturer that builds this category of planes (they are not).
Boeing has an issue in their planes that the A350 doesn't have. So if the price of 787's goes up because it needs to go from unsafe to safe, then airlines can buy A350s instead.
Boeing has an issue in their planes that the A350 doesn't have. So if the price of 787's goes up because it needs to go from unsafe to safe, then airlines can buy A350s instead.