This is another one of those things that Civ needs to improve on. Goverments are a very good example, but there's more. It's always taken too long in Civ to catch up in technology, as first-hand experience of a neighbour's or enemy's superior discoveries doesn't give any bonus in research.
In Civ3, every additional nation that has a tech, grants bonuses to other nations researching that tech. Only the first nation to research a tech has to actually pay full research price.
I never had a problem with this. I always fought the latest infantry since I've reinstalled.
Is your game patched?