The elf girl got "Otherworld common sense skill (Otherworldly Sense)", while the other two did not, means those boys know nothing, AT ALL. Currency included, heck, they don't know the currency name there, and how much money in their possession, until Elf girl told them. So yeah, they will be fucked without Elf girl helping them.
What is more suspicious? A lie created by the Girl whose brain is above than those two boys *glancing at their reincarnation point* and knowing the common sense or some ignorant demi-human + elf guy?