[Zurai]

In general, the cheapest per point of research (other than independants/heroes/etc that you can't depend on getting every game...) are your weak, 1 path mages. This is because every mage character (other than sages) have a base of 3 research, +1 per point in each path. So, if you can hire a 1 path, 4 research mage for 70 gold, or a 4 path, 7 research mage for 300 gold (made up amounts, but fairly accurate in general)... 2 1-path mages are half as expensive as a single 4-path, but have 1 point higher research. This effect is maginified considerably with a positive magic scale.

With a large drain scale (-3), it turns the other way around. Your 1-path mage would have 1 research, while your 4-path would have 4. You'd have to hire 4 1-paths to equal a single 4-path, and they'd cost you 20 more gold.


So, in general, your cheapest national mages are your best bulk researchers. Obviously if you can *afford* to buy the bigger ones, do so, but building cheapo national mages at 2-3 castles a turn is a good way to start the research juggernaut going a reasonable price.