diff --git a/internal/logic/public/order/promoPricing.go b/internal/logic/public/order/promoPricing.go
index 77b6e93..a1d9133 100644
--- a/internal/logic/public/order/promoPricing.go
+++ b/internal/logic/public/order/promoPricing.go
@@ -40,8 +40,8 @@ func calculatePurchasePrice(
 		if err != nil {
 			return nil, err
 		}
-		if promoResult != nil && promoResult.Eligible && promoResult.PromoPrice < unitPrice {
-			result.PayableBase = promoResult.PromoPrice * quantity
+		if promoResult != nil && promoResult.Eligible && promoResult.PromoPrice < originalPrice {
+			result.PayableBase = promoResult.PromoPrice
 			result.PromoRuleId = promoResult.RuleID
 			result.PromoDiscount = originalPrice - result.PayableBase
 			result.PromoPrice = promoResult.PromoPrice
diff --git a/internal/logic/public/order/promoPricing_test.go b/internal/logic/public/order/promoPricing_test.go
index fc89213..12456d2 100644
--- a/internal/logic/public/order/promoPricing_test.go
+++ b/internal/logic/public/order/promoPricing_test.go
@@ -66,7 +66,7 @@ func (m fakePromoModel) Transaction(context.Context, func(*gorm.DB) error) error
 	return nil
 }
 
-func TestCalculatePurchasePricePromoSkipsPercentDiscount(t *testing.T) {
+func TestCalculatePurchasePricePromoUsesQuantityTierTotalPrice(t *testing.T) {
 	svcCtx := &svc.ServiceContext{
 		DB: &gorm.DB{},
 		PromoModel: fakePromoModel{rules: []*promo.RuleWithPrice{
@@ -77,7 +77,7 @@ func TestCalculatePurchasePricePromoSkipsPercentDiscount(t *testing.T) {
 					Type:    promo.RuleTypeCampaign,
 					Enabled: true,
 				},
-				PromoPrice: 600,
+				PromoPrice: 279,
 			},
 		}},
 	}
@@ -87,9 +87,9 @@ func TestCalculatePurchasePricePromoSkipsPercentDiscount(t *testing.T) {
 		svcCtx,
 		1,
 		2,
-		1000,
-		3,
-		[]types.SubscribeDiscount{{Quantity: 3, Discount: 50}},
+		100,
+		7,
+		[]types.SubscribeDiscount{{Quantity: 7, Discount: 50}},
 		true,
 		true,
 	)
@@ -97,11 +97,11 @@ func TestCalculatePurchasePricePromoSkipsPercentDiscount(t *testing.T) {
 		t.Fatalf("calculatePurchasePrice returned error: %v", err)
 	}
 
-	if result.OriginalPrice != 3000 {
-		t.Fatalf("OriginalPrice = %d, want 3000", result.OriginalPrice)
+	if result.OriginalPrice != 700 {
+		t.Fatalf("OriginalPrice = %d, want 700", result.OriginalPrice)
 	}
-	if result.PayableBase != 1800 {
-		t.Fatalf("PayableBase = %d, want 1800", result.PayableBase)
+	if result.PayableBase != 279 {
+		t.Fatalf("PayableBase = %d, want 279", result.PayableBase)
 	}
 	if result.DiscountAmount != 0 {
 		t.Fatalf("DiscountAmount = %d, want 0", result.DiscountAmount)
@@ -109,8 +109,11 @@ func TestCalculatePurchasePricePromoSkipsPercentDiscount(t *testing.T) {
 	if result.PromoRuleId != 9 {
 		t.Fatalf("PromoRuleId = %d, want 9", result.PromoRuleId)
 	}
-	if result.PromoDiscount != 1200 {
-		t.Fatalf("PromoDiscount = %d, want 1200", result.PromoDiscount)
+	if result.PromoDiscount != 421 {
+		t.Fatalf("PromoDiscount = %d, want 421", result.PromoDiscount)
+	}
+	if result.PromoPrice != 279 {
+		t.Fatalf("PromoPrice = %d, want 279", result.PromoPrice)
 	}
 }
 
@@ -125,7 +128,7 @@ func TestCalculatePurchasePriceIgnoresInvalidPromoPrice(t *testing.T) {
 					Type:    promo.RuleTypeCampaign,
 					Enabled: true,
 				},
-				PromoPrice: 1000,
+				PromoPrice: 3000,
 			},
 		}},
 	}