OTOH, according to the Errata, it only costs 3 BP per Charm if the Charm being purchased is from a Caste or Favored Ability.  And as far as I can tell, Spells don't cost more for Terrestrials than they do for Solars.  Unless Spells count as Charms for them.  But reading from the experience table in the corebook, it seems that Spells and Charms are two different things.