I heard if you build a water pump on one side of the map, and another onthe other side, you fast travel to one side, collect 300 purified waters for 40caps value each, fast travel to the other side, 300 waters, just go back and forth and you'll have millions of caps within an hour, you basically don't have to scavenge or loot anything ever just buy it at merchants. The annoying part is waiting for two days for vendors to restock caps