cashshop_ui_itemid_as_currency.diff (see: https://rathena.org/board/topic/119249-cash-shop-item-payment-instead-of-cash-points/)

cashshop_ui_itemid_as_currency.diff

diff --git a/conf/battle/items.conf b/conf/battle/items.conf
index be5e6448d..ce1e6c1de 100644
--- a/conf/battle/items.conf
+++ b/conf/battle/items.conf
@@ -141,3 +141,11 @@ min_shop_buy: 1
 // Minimum sell price of items at a normal shop
 // Officially items can be sold for 0 Zeny
 min_shop_sell: 0
+
+// Instead of Cashpoints in Cashshop UI (interface)
+// Use ITEMID with ID below. The item must exists in the game
+// The item must have tradable flags, etc like a normal item
+// Instead of cashpoints will be consumed the item from players inventory
+// Set it to 0 if you wish completely disable the system.
+// Max ID = 65k
+cashshop_currency_itemid: 505
diff --git a/src/custom/battle_config_init.inc b/src/custom/battle_config_init.inc
index e47aca9be..8e6557eb8 100644
--- a/src/custom/battle_config_init.inc
+++ b/src/custom/battle_config_init.inc
@@ -11,3 +11,5 @@
  *	 { "name", &battle_config.<variable name>, <default value>, <minimum value>, <maximum value> },
  **/
 
+// Cashshop UI item currency shop:
+{ "cashshop_currency_itemid",                     &battle_config.cashshop_currency_itemid,                  0,      0,      MAX_ITEMID,              },
diff --git a/src/custom/battle_config_struct.inc b/src/custom/battle_config_struct.inc
index 017d99d07..3b708765a 100644
--- a/src/custom/battle_config_struct.inc
+++ b/src/custom/battle_config_struct.inc
@@ -12,3 +12,6 @@
  *	 <datatype> name;
  **/
 
+
+// Cashshop currency ItemID shop
+int cashshop_currency_itemid;
diff --git a/src/map/cashshop.cpp b/src/map/cashshop.cpp
index df26abde7..65058a7cf 100644
--- a/src/map/cashshop.cpp
+++ b/src/map/cashshop.cpp
@@ -564,10 +564,32 @@ bool cashshop_buylist( struct map_session_data* sd, uint32 kafrapoints, int n, u
 		return false;
 	}
 
-	if(pc_paycash( sd, totalcash, kafrapoints, LOG_TYPE_CASH ) <= 0){
-		clif_cashshop_result( sd, 0, CASHSHOP_RESULT_ERROR_SHORTTAGE_CASH );
-		return false;
+	// Custom code for using instead of cashpoints itemID as a currency in cashshop UI shop.
+	if(battle_config.cashshop_currency_itemid)
+	{
+		struct item_data *id_cash_currency = itemdb_search(battle_config.cashshop_currency_itemid);
+		if (!id_cash_currency)
+		{
+			clif_cashshop_result(sd, 0, CASHSHOP_RESULT_ERROR_SHORTTAGE_CASH);
+			ShowError("cashshop_currency_itemid: %d itemID not exists in the game, try another one.\n", battle_config.cashshop_currency_itemid);
+			return false;
+		}
+		int item_idx = pc_search_inventory(sd, battle_config.cashshop_currency_itemid);
+		if (item_idx < 0 || pc_delitem(sd, item_idx, totalcash, 0, 0, LOG_TYPE_CONSUME))
+		{
+			clif_cashshop_result(sd, 0, CASHSHOP_RESULT_ERROR_SHORTTAGE_CASH);
+			return false;
+		}
+	}
+	else // Original Function
+	{
+		if (pc_paycash(sd, totalcash, kafrapoints, LOG_TYPE_CASH) <= 0)
+		{
+			clif_cashshop_result(sd, 0, CASHSHOP_RESULT_ERROR_SHORTTAGE_CASH);
+			return false;
+		}
 	}
+	// Custom code for using instead of cashpoints itemID as a currency in cashshop UI shop.
 
 	for( i = 0; i < n; ++i ){
 		unsigned short nameid = *( item_list + i * 5 );

How apply?

git apply --reject cashshop_ui_itemid_as_currency.diff

Or with SourceTree -> Apply Patch.