Barrier:
Level 1-Already Unlocked
Level 2-To Unlock: Spend $2,000 on barriers.
Level 3-To Unlock: Spend $8,000 on barriers.
Level 4-To Unlock: Spend $20,000 on barriers.
Level 5-To Unlock: Spend $45,000 on barriers.
Level 6-To Unlock: Spend $75,000 on barriers.
Level 7-To Unlock: Spend $120,000 on barriers.
Level 8-To Unlock: Spend $170,000 on barriers.
Decoy:
Level 1-To Unlock: Spend $2,000 on barriers.
Level 2-To Unlock: Spend $5,000 on decoys.
Level 3-To Unlock: Spend $20,000 on decoys.
Level 4-To Unlock: Spend $35,000 on decoys.
Level 5-To Unlock: Spend $75,000 on decoys.
Level 6-To Unlock: Spend $110,000 on decoys.
Level 7-To Unlock: Spend $170,000 on decoys.
Sentry:
Level 1-To Unlock: Spend $35,000 on decoys.
Level 2-To Unlock: Spend $10,000 on sentries.
Level 3-To Unlock: Spend $30,000 on sentries.
Level 4-To Unlock: Spend ? on sentries.
Level 5-To Unlock: Spend $90,000 on sentries.
Level 6-To Unlock: Spend $135,000 on sentries.
Turret:
Level 1-To Unlock: Spend $20,000 on barriers.
Level 2-To Unlock: Spend $15,000 on turrets.
Level 3-To Unlock: Spend $50,000 on turrets.
Level 4-To Unlock: Spend $90,000 on turrets.
Level 5-To Unlock: Spend $140,000 on turrets.
Level 6-To Unlock: Spend ? on turrets.
Level 7-To Unlock: Spend $270,000 on turrets.
Level 8-To Unlock: Spend $360,000 on turrets.
Silverback:
Level 1-To Unlock: Spend $170,000 on barriers.
Level 2-To Unlock: Spend $200,000 on silverbacks.