The ship would be constructed by Andonia, with the assistance of Pax Pacis and some money from the Empire. Charities will be set up to help reduce the cost to the Empire as well. This would make it not that expensive, but still not cheap. The benefits outweigh the costs. There is the diplomatic and public opinion benefit, and there is the benefit of saving more lives during conflicts. If your brother was lying on a battlefield, bleeding to death because there was no hospital ship to help him, would you still say that the hospital ships are a bad idea?