A karrazan costs 213 gold, gives twelve attack power and +2 combat speed.

An elementium karrazan costs 12000 gold, gives twelve attack power, and no extra combat speed.

Exactly what am I paying 60 times as much gold for?

Also, is it correct that non-elementium karrazans cannot be given to regular troops (for kingdoms, at least)?  I see enemy (empire) units with them all the time.

EDIT:  Disregard the second question.  I double-checked in-game and it looks like only Sions get the karrazan.