Perhaps the unit earns 20 xp for the kills it achieves. That makes sense, since there must be some kind of point system based on each unit killing things.
Now it makes less sense to receive 20 xp for everything the unit builds, but it does make sense that the player receive xp for training the unit. Considering that it costs 200 food, there needs to be some kind of exchange/reward for that cost.
ES would not make all civilizations the same in terms of rushing/booming/turtling. Prior games have certain civs. that are good at different strategies.
Consequently, it is viable that each civ. receives different XP bonuses. So the French get XP a little faster just from creating Coureur des Bois, without engaging in any battles, resulting in earlier access to shipments.
Then again, the game is not finished yet, and all these things will probably change.
One other thing, I do not think the unit costs XP, since XP are not listed under cost.
[This message has been edited by fhertlein (edited 05-24-2005 @ 03:21 PM).]