Boron: Conjuration 9 is HIGH. At that level summons are meant to be very cost-effective, worth every gem you use. Wights are. (Sea) Trolls are nice mid-game, and might be the one thing that forces you to defend instead of researching, or that kills you before you get access to Wights. Also, if you have the right mages and want to use them for summoning instead of researching, you can summon one trolls for one gem. With, say, 10 national mages summoning trolls for three turns you get 30 trolls for 30 gems. It is slower, but very cost-efficient in gems, although less so in mage time. All those mages could be doing something else, like forging, fighting or researching, or searching for sites.
Besides, recruiting trolls for 0gp/piece would become boring after a while, don't you think?
Re: upkeep
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