Its really a simple test:
I put all the ability points i can into diplomacy and play as terran alliance with one test dummy(drengin). I research the universal translater tech and send my survey ship to drengin territory. after I make contact go to the trade screen try to trade 100 bc to to their 100 bc(i got there after only a few turns so they still have 1567 bc ,after quick buying everything, while i have 5036 bc).
it says i have a incredible ability in diplomacy compared to their but my 136 bc is equal to their 100.
Okey they have less money then me which to them makes their money more valuable. So i set the galaxy to tiny and stars rare and ctrl+n a few times before they are right next to me i make contact immediately and this time i am playing custom race so i have universal translater in pre-selected techs. Their money is still more valuable then mine even though they . So they have a 36% advantage in diplomacy even though i have maximum ability points in diplomacy. and they consider me more powerful and its jan 1 2225.
I dont want my money to be worth more then theirs but atleast equal. Tried the same thing with influence points too, slightly different results but still favoring them.