Dev needed a hight number and chose this one. Maybe he/she felt evil for making ethereal creatures almost immune to physical attacks?
Ghosts are supposed to be kind of immune to normal attacks, you know, for being ethereal and all. Maybe use magic next time? Or hire a mage? Or use a potion that deals fire damage? Or use a weapon that deals magic/elemental damages when in the cemetary?
I mean if your character can't deal with ethereal creatures going in the cemetary without a backup plan is a pretty bad idea...