While you are correct that it will likely be expensive, it is important to note that Descovy is an existing PreP pill that Gilead makes. So the cost of the new shot is yet to be determined, but the company has been criticized for the cost of their current PreP medication option.
It is also important to note that anyone with insurance in the United States will pay nothing, as the Affordable Care Act requires insurance to cover all PreP medications at no cost to patients. The pricing will only affect those who have no insurance at all, which makes this criticism all the more important to help this new medication reach those who would be the worst affected if they were to contract HIV.