The fault in the whole changing price argument is SE didn't change the price of the subscription. What changed is the exchange rate. The exchange rate just happened to change the pricing of the sub for certain people in a negative way.(Truth be told if this occurred and let's say SE for some reason decided to have BRL pay 14.99 a month aka $4.77/month, no one would make a peep because it's in their favor.)

Basically the 30 days warning would occur if saying FFXIV decided to go from 14.99/month to 16.99 a month, that's changing the price of the subscription fee. What occurred with Russia and Brazil is a change in pricing due to currency rate conversion. What appears to be the reality is due to your weaker currency you are now paying more for your sub, but this isn't the result of SE changing the subscription fee, they changed the worth of your currency to be more in tune with the global market. And to that it is accurate. 28.99 in BRL was $9.23, and now as you said it's 41.99 which brings you to $13.36, which better represents the global cost.

I'm just saying, SE has no reason to release a 30 day warning about this because what occurred is the result of a currencies loss in value rather than them changing the price of subscription for all players otherwise everyone would be facing a price increase currently, but this is only hitting people of certain currency.