How is unit upgrade cost calculated?

[Strategist83]

Much to my surprise, I found that I could upgrade my riflemen to infantry for only 97 gold. How can this be? Usually, upgrade costs are way higher. So, now I'm speculating on how upgrade cost is calculated.

[Nacht]

As far as my observations go it's:

(new units hammers cost - old units hammers cost) * 3 + 25

That doesn't explain your 97 of course, should be 205.

[Nacht]

btw, I play marathon, so things could be different at other speeds.

[Solver]

That's the correct formula, interestingly enough. Only the 3 and the 25 come from XML, and can be changed.

[Stickyman]

Does this indicate to you that the game considers 3 gold = 1 hammer

[Solver]

For upgrade purposes .

[drsparnum]

Sometimes 2 hammers = 1 gold. Like when you build research (as far as I recall).

[Nacht]

Originally posted by drsparnum
Sometimes 2 hammers = 1 gold. Like when you build research (as far as I recall).

That would be 2 hammers = 1 commerce.

[Wanderlust]

Did you have the Kremlin?

[Older than Dirt]

It should cost more to maintain antique muskets and to pay the extra medical expenses of all the old men in the obsolete unit; just euthenize the soldiers (do not do this to a named unit or you may feel a twinge of regret).

[Nacht]

Originally posted by Wanderlust
Did you have the Kremlin?

The kremlin hasn't anything to do with upgrade costs.

[marvinkosh]

Yes, the Kremlin grants your Civ a relatively short-lived 50% discount on rushing cost. I don't know though if this refers only to gold rushing or also to pop rushing.

[Badtz Maru]

Originally posted by marvinkosh
Yes, the Kremlin grants your Civ a relatively short-lived 50% discount on rushing cost. I don't know though if this refers only to gold rushing or also to pop rushing.

The bonus to gold rushing has nothing to do with unit upgrade costs, only with the creation of new units.

[marvinkosh]

Originally posted by Badtz Maru
The bonus to gold rushing has nothing to do with unit upgrade costs, only with the creation of new units.

I know, I was elaborating on what The Kremlin actually does do, which is save you a pile of gold that can, funnily enough, be put to good uses

[Strategist83]

Originally posted by Nacht
As far as my observations go it's:

(new units hammers cost - old units hammers cost) * 3 + 25

That doesn't explain your 97 of course, should be 205.

This formula means upgrading units is extremely expensive in the early game but manageable later on. What exactly is the thinking behind that? Shouldn't upgrading be relatively equally expensive at all times?