hmm okay, but this is what the wiki itself says:
so i'm guessing the wiki just isn't updated or something?
It is just bad spelling, it means that upgrading after you have the 41 technology research is cheaper than every time when you get the new tech...
I think that with every neew tech, upgrade days and IC are reduced by half.
So, lets say, if an infantry needed 10ic and 10 days to upgrade (fictional numbers), it would be:
Every tijme you research one tech upgrade:
18-->36 : 10*10 Icdays=100
36-->39 : 10*10 Icdays=100
39-->41 : 10*10 Icdays=100
Total =300
While, if you start upgrading after you have researched all the techs till 41:
18-->36 : 2.5*2.5 Icdays=6.25
36-->39 : 5*5 Icdays=25
39-->41 : 10*10 Icdays=100
Total = 131.25