Why am I paying a champion for his supporting units?

What the title says.  There's an enormous jump in price from a level 5 champion (no supporting units, ~3-400 gold) and a level 7 unit (1190 gold, with 1 fire elemental support unit).  That's after the Adventurer's guild reduced the cost, too.  With that kind of money, I could buy an army big enough to wipe out 7 opposing factions at once.  Bring down the costs on level 7+ champions.