diff --git a/OpenRa.Game/OpenRa.Game.csproj b/OpenRa.Game/OpenRa.Game.csproj
index 84f9a6276a..b427fe0c01 100644
--- a/OpenRa.Game/OpenRa.Game.csproj
+++ b/OpenRa.Game/OpenRa.Game.csproj
@@ -118,6 +118,7 @@
     <Compile Include="Support\PerfHistory.cs" />
     <Compile Include="Sync.cs" />
     <Compile Include="Traits\Attack\AttackOmni.cs" />
+    <Compile Include="Traits\CustomSellValue.cs" />
     <Compile Include="Traits\World\BridgeLoadHook.cs" />
     <Compile Include="Traits\World\ChoosePaletteOnSelect.cs" />
     <Compile Include="Traits\World\Country.cs" />
diff --git a/OpenRa.Game/Traits/Activities/Sell.cs b/OpenRa.Game/Traits/Activities/Sell.cs
index e5189bac57..4887503158 100644
--- a/OpenRa.Game/Traits/Activities/Sell.cs
+++ b/OpenRa.Game/Traits/Activities/Sell.cs
@@ -15,7 +15,8 @@ namespace OpenRa.Traits.Activities
 
 		void DoSell(Actor self)
 		{
-			var cost = self.Info.Traits.Get<BuildableInfo>().Cost;
+			var csv = self.Info.Traits.GetOrDefault<CustomSellValueInfo>();
+			var cost = csv != null ? csv.Value : self.Info.Traits.Get<BuildableInfo>().Cost;
 			var hp = self.Info.Traits.Get<OwnedActorInfo>().HP;
 			var refund = Rules.General.RefundPercent * self.Health * cost / hp;
 
diff --git a/OpenRa.Game/Traits/Building.cs b/OpenRa.Game/Traits/Building.cs
index f11a302276..698106345a 100644
--- a/OpenRa.Game/Traits/Building.cs
+++ b/OpenRa.Game/Traits/Building.cs
@@ -96,8 +96,10 @@ namespace OpenRa.Traits
 
 			if (remainingTicks == 0)
 			{
+				var csv = self.Info.Traits.GetOrDefault<CustomSellValueInfo>();
+				var buildingValue = csv != null ? csv.Value : self.Info.Traits.Get<BuildableInfo>().Cost;
 				var maxHP = self.Info.Traits.Get<BuildingInfo>().HP;
-				var costPerHp = (Rules.General.URepairPercent * self.Info.Traits.Get<BuildableInfo>().Cost) / maxHP;
+				var costPerHp = (Rules.General.URepairPercent * buildingValue) / maxHP;
 				var hpToRepair = Math.Min(Rules.General.URepairStep, maxHP - self.Health);
 				var cost = (int)Math.Ceiling(costPerHp * hpToRepair);
 				if (!self.Owner.TakeCash(cost))
diff --git a/OpenRa.Game/Traits/CustomSellValue.cs b/OpenRa.Game/Traits/CustomSellValue.cs
new file mode 100644
index 0000000000..93eca979b0
--- /dev/null
+++ b/OpenRa.Game/Traits/CustomSellValue.cs
@@ -0,0 +1,17 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace OpenRa.Traits
+{
+	// allow a nonstandard sell/repair value to avoid
+	// buy-sell exploits like c&c's PROC.
+
+	class CustomSellValueInfo : StatelessTraitInfo<CustomSellValue>
+	{
+		public readonly int Value = 0;
+	}
+
+	class CustomSellValue {}
+}
diff --git a/mods/cnc/structures.yaml b/mods/cnc/structures.yaml
index 3c4202dd80..90f5c966f5 100644
--- a/mods/cnc/structures.yaml
+++ b/mods/cnc/structures.yaml
@@ -58,6 +58,9 @@ PROC:
 	StoresOre:
 		Pips: 17
 		Capacity: 1000
+	CustomSellValue:
+		Value: 600
+		
 SILO:
 	Inherits: ^Building
 	Buildable:
diff --git a/mods/ra/rules.yaml b/mods/ra/rules.yaml
index 4e4e206fec..bca1563d4a 100644
--- a/mods/ra/rules.yaml
+++ b/mods/ra/rules.yaml
@@ -1354,7 +1354,9 @@ FACT:
 	Production:
 		Produces: Building,Defense
 	ConstructionYard:
-	IronCurtainable:
+	IronCurtainable: 
+	CustomSellValue:
+		Value: 1000
 
 PROC:
 	Inherits: ^Building
@@ -1380,6 +1382,8 @@ PROC:
 		Pips: 17
 		Capacity: 2000
 	IronCurtainable:
+	CustomSellValue:
+		Value: 600
 
 SILO:
 	Inherits: ^Building