Purchasing a skill from a trainer (Signet of Capture or otherwise) increases in
gold cost with each skill bought, up to a maximum of 1 platinum.

Purchasing a skill from a Priest of Balthazar costs 1000 Faction points, or
3000 Faction points for an Elite skill.  You earn Faction points from fighting
in any PvP combat.  Note that skills unlocked from a Priest of Balthazar are
NOT given to your PvE Roleplaying character.  They are unlocked for the purpose
of creating a PvP-only character, just like unlocking skills and upgrades in
regular PvE play.