About the unit upgrade differences between the civilizations.

https://ageofempires.fandom.com/wiki/Unit_upgrade_(Age_of_Empires_III)

I recently found the above page about the unit upgrades in AoE3. It's very well organized, so I hope you guys take a look.

By the way I found that the upgrade costs of the Natives are much lower than those of Europeans and Asians. If you finished the 4th age upgrade, you would consume 800 wood / 800 coin for Europeans and 800/700 for Asians, but you would consume only 600/300 for the Natives.

And the 3rd age upgrades of the Natives add 25% HP and damage, while those of Europeans and Asians add just 20%. Though the upgrades of all civilizations are set at 50% in the 4th age, the efficiency of the 3rd age upgrades is way better for the Natives than Europeans and Asians.

I know not all civilizations can be the same, and I know that the developers intentionally did this to make a difference between the civs. But this inconsistency confuses me. Is there a good reason why the Natives should have particularly better upgrades? Did the developers intentionally give the Natives better upgrades because their economy is not good?