That is the case either way. The ratio is constant. I believe it is anyhow. There are probably benefits that the AI is not getting enough to keep up on easier settings and that's just a matter of how it all plays out in the wash that it tends to make it harder for them to spread faster on easier settings. It would take a lot of auditing to see how it happens exactly.
It is constant for players on Noble and higher handicap.
Ai gets stronger reduction on construction costs than tech costs on higher handicaps.
I made table some time ago.
Here are AI modifiers for units, buildings and techs.
In brackets I added ratio of unit and building cost modifier to tech modifier.
Prince ---- 90 92 95; (0.95, 0.97) - Close to current build costs.
Monarch - 80 84 90; (0.89, 0.93)
Emperor - 70 76 85; (0.82, 0,89)
Immortal - 60 68 80; (0,75, 0,85)
Deity -------- 50 60 75; (0,67, 0,80)
Nightmare - 30 44 65; (0,46, 0,68) - Easy to expand high and wide for AI.
Compared to old system handicaps got harder except for tech cost on deity and nightmare.
This means effectively lowered construction cost globals for units and buildings.
And we know, that low construction cost is good for everyone (balance is other matter).
AI will build more buildings and units, when they are researching things.
Also this helps boost research rates too.
If building/unit costs gets increased, then things get easier for players.
Units, building and tech cost reduction steps are in 10/8/5 steps per handicap increase.
I added my Excel spreadsheet.
Maybe tech global is too low or construct global is too high for Noble AI?
On other hand StrategyOnly plays on Warlord, and in his savegame all AIs expanded.
I guess someone is
efficient.
I'll test game on Noble/Blitz/Standard.
During my test some AIs are wasting time on process and lose scouts/wanderers to animals.
They should always build all buildings, if their cost is less than 25% of current production rate, and if they doesn't worsen properties and its maintenance isn't too high.
Exception would be resource producers, if they don't have given resource yet.
This brute force solution should help AIs especially on higher handicaps and later eras, where are lengthy building chains.
And since that brute force solution would look only for current production, buildings, that are buildable now, properties and resources it shouldn't slow down this game too much.
Also its better to waste turn on 4 cheap buildings than on process.
That is when you reach Classical era, then you should have all buildings from Prehistoric era where it is possible.
Arrived to 100th turn.
AIs reached Ancient Era, but they didn't use tribe to build cities.
I guess they don't want to waste time on tribes on Noble/Blitz/Standard combo.
I added autosave on 150th turn.
Will do Nightmare autorun test.
On this handicap AI will train/build/research things 3.33x/2.27x/1.54x faster than player.
Most of AIs reached Ancient Era on 50th turn and built two cities.
It appears player civ is treated as player during autorun, so basically I'm testing 6 AIs and there are 7 civs in total.
AIs build multiple cities on 130 something turn then game froze.