I don't think that a vampire cure is available in dungeons and dragons unless a god fulfills a wish, which from my understanding AO will NOT allow the current set of gods/goddesses to do. So that is why God Gale can not cure either the sunlight curse or vampirism. What Boo is talking about is things used on other worlds within the universe but I am not sure that Larian will use it, tbh? Due to the fact that it isn't even in the game at all. You can ask God Gale for the sunlight cure, not a vampirism cure. There is no dialogue about curing his vampirism at all. The magic required to do the vampire cure is rare for materials, items, etc and that is why it is extremely expensive. You would also have to travel to another planet to get the items, so that is beyond difficult for sure due to the power needed just to travel to another planet is EXTREME magic & performed by very few individuals in the universe. In all honesty, I don't know if Astarion himself would want it though....that would break his character that much more. Just my humble opinion backed up with lore knowledge.
