[PvK]

I see Zath's line of argument, but it's overstated and focused on one perspective. The mages are not the only valuable units produced, and you'll generally get several mages in the effort used to get an E2 or E3. Saying the other mages and troops aren't "worthwhile" is a narrow argument. Even if your main purpose is to get an E2-3 mage, the fact that you get other mages and troops doesn't mean they have zero value. The chance that you may get more mages and units than you expect, or that you may get them sooner or cheaper, also has value - it just depends on whether you choose that value, or whether you prefer sure things, which is a preference, not an absolute value. As for "just empowering a mage" in Earth magic, that's not so easy when you are a nation who lacks earth magic, and it results in an existing mage getting better, not getting a bunch of other mages and unique troops as part of the deal.

From a balance and flavor perspective, I'd say it's good that it is uncertain and has significant cost, because otherwise any nation able to cast Hidden In Snow could be considered to also have E2-3 magic, which would blur the distinct strengths and weaknesses of the nations' path variety.

I like the idea of making it more expensive and giving more of the unfrozen troops.