Brutals haven't declined much in value, but we'll see how that goes considering zombies give the best exp currently. I'm keeping my fingers crossed.
It could bring down the price of brutals, but also diamonds as well, since they're typically acquired in the same place. But more harvesting also means more platinum being spent, more sapphires being melted down, and so forth. My worry is that increased farming could also bring down the value of those things as well, since it all works in a kind of 'loop':

Sapphires -> Dusts -> Platinum -> Scrolls -> Sapphires

Typically, every time you hit the 'Sapphires' part of the loop, it also includes spawning Diamonds, Brutals, and even more Platinum. (Which, if unspent, can lead to problems.)

Yea, they're holding their "conscious value" relatively well considering they are more regularly being introduced to the market than any time previous (not including stints involving Jon - only natural introduction). Before any confusion can be made concerning the decline in brutal value - it's very important to note that I mean the CONSCIOUS VALUE of brutals and not their currency value - the value a person consciously and emotionally places on an item.

Y'know, Scrooge McDuck could teach GK players a thing or two about inflation.

Close enough.

Lylic and co. managed to do this successfully back in 06 bringing them from 10d back down to 5d. Good luck with your conquest.

I don't recall that