By the way, the cost reduction isn't really a cost reduction, depending on how you look at it. Basically, each spellcasting power you get includes what is basically a free level of refinement worth of focus slots for each half of the spellcasting spectrum. So Evocation and Thaumaturgy each cover half of the spectrum, and each include one free refinement worth of focus slots (ie, 2). Sponsored Magic, on its own, covers the whole spectrum, and includes two refinement worth of slots (four). If you get Sponsored magic and Evocation, you have an overlap, so you refund one of those levels of refinement (but don't get the extra free focus slots, either).
At least, it makes sense to me that way, but it might be even more confusing to others.