Returns the cost to purchase a trainer service
See also Trainer functions.
index- Index of an entry in the trainer service listing (between 1 and
moneyCost- Amount of money required to purchase the service (in copper) (
talentCost- Number of talent points required to purchase the service (generally unused) (
skillCost- 1 if purchasing the service counts against the player's limit of learnable professions; otherwise 0 (