Exaclty, look at a goblin which is CR1/4th. We had PC's fighting a huge group of goblins. If there are 24 goblins in the encampment that's 6 CR1's, or 1800xp for a 3rd level party.
Now we can modify them a bit using the NPC 15, 14, 13, 12, 10, 8 method. Make them a 6 War3's, and it's still...