All right, Abramo sees his mistake: He tried to find twentieth-century venture capital in an economy that, although it has magic these Extremely Advanced Technological Constructs, is clearly very unproductive by his standards and not immensely financially sophisticated (*) either. He will turn, instead, to - ahem - adventure capital. It appears that the Extremely Advanced Technology can also be used to create objects which show permanent effects, as opposed to being one-use; and such objects are both commonly wielded by cultists as weapons, and saleable for prices that are high relative even to large amounts of military equipment. If every cultist leader killed can fund say half a dozen well-equipped mercenaries, then - well, this is a war of skirmishes and scuffles, by the standards he's used to. At that rate he can soon put together a vast host - say a hundred men or so.
Abramo's not going to worry about the effects of all this liquidity entering the disaster-struck local economy which, so far as he can tell, is currently not producing anything except perhaps fighting men, nor about how it is doing so. There seem almost to be two separate economic tiers here, one that deals in onions and fish and chickens, and one that deals in weapons of war, and their prices are almost entirely decoupled. As though producing more breastplates and pikes and boots and winter clothes somehow did not funge against grain and potatoes and turnips... or as though Kenabres is connected by this Extremely Advanced Technology to some humongous reservoir of both, too large for its prices or its productive capacity to be much affected by what Kenabres chooses to import in exchange for exporting the Extremely Advanced Technological Objects ok fine he'll just call them "magic weapons" like everyone else. As he was saying: Kenabres is apparently connected to some huge outside economy which can absorb its (presumably) finite stock of magic weapons without making much of a dent in its prices, and if he controls that export then he can choose what gets imported in exchange - and perhaps even avoid the immense inflation that so much money chasing a finite and diminishing stock of goods must inevitably cause. He'll just avoid having the money enter the economy in the first place, the so-called "gold pieces" will in effect be an accounting device between him and the Outside Economy, an intermediate step that makes it easy for him to figure the exchange rate between, say, pike-and-breastplate to equip a fresh recruit, or wagons of flour to feed existing ones.
And in any case - needs must when the demons drive. If he doesn't win this war fast, there won't be time for inflation to cause widespread starvation. Instead there will be widespread starvation among the demons when they're done eating the humans.
(*) Abramo is, actually, a country bumpkin on this point; the financial industry he's thinking of doesn't even have derivatives trading for retail customers, or indeed standardised options contracts. But yes, routinised joint-stock companies and stock exchanges operated by radio and telephone does in fact put it ahead of Golarion, or at least Mendev, in spite of the best efforts of Abadar's churches.