I don't get the fixation on extreme high quality centers.
There are many places in the game where number of soldiers is important, or more important than quality. Takeovers, looting, civil work and many others. Cheap units that you can mass-recruit have always had a place, and the best advise in my book was the one telling you to look for what the realm already has and try to cover out what it doesn't.
And never forget that the next try could get you something worse. So if you get a long-range archer unit with very low armour, you just might want to suck it up and keep it, because who knows how long you have to try to get one with the same range an better armour.
Dirt cheap (calculated in gold/man) and top stats are the two things that realms should strive for.
Yes, as you said, many things only consider troop number. But in many wars, none of these things will be done. And if all you plan on doing is fighting, you are much better off with a small army of elite troops than a horde of cheap troops.
