Ok, now that I see what you're driving at, I can kinda see the point.
For the comment
why should I trade 2 units for 1 right now at 180 hammers for a 100-120 hammer building that only gives 4/3 for 1 unless I use them immediately?
what i meant is that right now, for 180 hammers, i can have a building that doubles the number of units I get - 2 for the price of 1. However, with the unready promotion, unless I use them to get them above level 4 I end up with 2% of the time the promo wearing of, and 1% of the time them going barbarian - therefore, for every 6 units that I build, I end up with it wearing off on approximately 4 of them, while the other 2 are going to end up being barbarian. Yes, this isn't quite exact, but last page someone posted about halflife (what you really should be looking at for these numbers).
As for the Calculations, you can test them with a hunter against a bear (I ended up testing them with a ranger against Gurid). With that ranger (actually, an astrian tracker with combat 4), gurid went from strength 22 to strength 13.4 or something like that (note, he had no promos). It doesn't work exactly like that, but I can't tell quite how, as shown by griffons constantly eating scouts (if it was straight 50%, a griffon and a scout would both be strength 2, but the griffon comes out at a different strength - I think at strength 3). Shock, anti-melee bonuses, etc, work in the exact same way as the ranger's anti-animal/anti-beast. Similarly, it shows in the calculations when you take and attack a city with a hunter, that the hunter recieves -20% strength because of his built in functions. Another big one that many people use here is assassins attacking a city - the assassin goes from strength 6/4 to strength 3/2. However, if the assasin recieves a 50% strength bonus (say from combat 2 and shield of faith), he returns to strength 6/4, showing how the bonuses are additive. Similarly, a hunter of strength 4 attacks a city at strength 3.2, unless it has combat 1 and then it is strength 4 attack.
Hope the calculations part helps.
-Colin