The costs you mention for this power seems extremely high.
The power is not sponsored magic (maybe it is in flavor terms, but not mechanically), it does not grant any form of channeling or ritual and does not provide access to sponsor debt (at least not that you described). At also does not seems to give any other bonus.
The power is closer to just allowing the character to craft/declare potions. I think there is a custom power that allows access to potions (or maybe full crafting) somewhere around here, I think it was called Bag of Tricks. It should cost around [-1] and give around 4 enchanted item slots (like refinement).
I found it (from Sancta's custom powers list):
BAG OF TRICKS [-1]
Description: For whatever reason, you have access to a few minor magical trinkets.
Skills affected: Contacts, Resources, Burglary, Lore.
Effects:
Enchanted Items: You have four potions, each with a strength equal to your Contacts, Resources, Burglary, or Lore skill. You may not increase their strength in any way. At the beginning of each session, you must declare which potions you have on hand.
More Trinkets [-1]. You have four additional potions. Furthermore, you may choose to leave potion slots open to be filled later with Declarations.