Tier 7 of 7
150,000 HP and up
A siege wave pays this when all of its zombies' HP adds up to this much. The horde setting moves a wave up or down the tiers.
Ground loot
A beaten wave leaves 2 kinds of item at the door, plus 1 more for every 20 kills (at most 8). Each kind comes 1 at a time, plus 1 for every 60 kills (at most 2).