My point, which I think you missed, is that it should never be cheaper to build a unit and then upgrade it, rather than to build the upgrade straight off.
But it is. For everyone, not just the Doviello.
Given a bit of testing, hammers from hurrying production seem to come at a cost of 3

per 1

. Trying to build something before it has had a chance to accrue at least one turns worth of hammer incurs a 50% increase to the multiplier, or 4.5

per 1

. I'm going to ignore that 50% increase in the next bit for clarity. If you want, imagine a city with 1 production at take off 3

from the total.
Warrior: 25

, 75

Axeman: 60

, 180

Champion: 120

, 360
Then, there's the upgrade cost. I don't know what fancy formula it uses, but the values are:
Warrior----->Axeman 75

Warrior----->Champion 195

Axeman----->Champion 125
The Doviello are mostly the same when it comes to the production costs with the slight difference of the battlemaster.
Beastman: 25

, 75

Sons of Asena: 60

, 180

Battlemaster: 150H

, 450
Why the battlemaster is more expensive then a champion is beyond me. Champions get a +25% vs melee. Battlemasters get a +50% on tundra. That's the only difference I can see. While its a larger bonus, it is far more situational and doesn't seem worth a 25% increase to

cost.
Anyways, Doviello upgrades are where the big differences hit.
worker----->Beastman 20

Beastman----->Sons of Asena 40

Sons of Asena----->Battlemaster 80
So beastmen roughly get a 50% (46.6%) decrease (40

vs 75

) to their upgrade cost. Sons of Asena get a a 36% reduction (80

vs 125

), but that's not considering the extra

a Battlemaster costs. When that's taken into account, you get roughly back into the 50% (55.5%) range.
Essentially, the Doviello upgrade scheme is like having ingenuity for free.
So, if its a balance concern, why are we not concerned about the ingenuity trait? Unlike the Doviello, any other civilization can continue to build their warrior units after bronze working. If they have the ingenuity trait, they can upgrade these units for less then the Doviello.
Warrior----->Axeman 38 gold
Warrior----->Champion 98 gold
Axeman----->Champion 63 gold
So, if the ingenuity trait isn't a balance issue, then Doviello being able to build beastmen throughout the game shouldn't be one either. Sons of Asena don't obsolete, so why beastmen?
The only time the Doviello upgrade system becomes truly evil is when they have the ingenuity trait. 20

for warrior to become a son? Yes please!
However, is it really any more evil then any of the other nasty combinations in the game?
It might be, actually. Maybe drop the base reduction the Doviello get from around 50% to around 30%. Thoughts?