Reduce the base fee on Polkadot System Chains (polkadot-fellows#398)

This PR reduces the base fee on all Polkadot system chains by half. As a
result, the base fee will be roughly 1/20 of the base fee on the
Polkadot relay chain.

This will make all transactions on (non-congested) system chains cheaper
and stimulate usage.

Among others, the change will push the transaction fees for transfers on
Asset Hub below $0.01 which is an important psychological threshold.

An initiative by ecosystem agents.

---------

Co-authored-by: Adrian Catangiu <[email protected]>
Co-authored-by: joe petrowski <[email protected]>

CHANGELOG.md

@@ -14,6 +14,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ### Changed
 
 - Bounties: Remove payout delay ([polkadot-fellows/runtimes#386](https://github.com/polkadot-fellows/runtimes/pull/386))
+- Polkadot System Chains: Reduce the base transaction fee by half
 
 ## [1.2.8] 03.07.2024
 

integration-tests/emulated/tests/assets/asset-hub-kusama/src/tests/teleport.rs

@@ -166,7 +166,7 @@ fn penpal_to_ah_foreign_assets_receiver_assertions(t: ParaToSystemParaTest) {
 				owner: *owner == t.receiver.account_id,
 				amount: *amount == expected_foreign_asset_amount,
 			},
-			RuntimeEvent::Balances(pallet_balances::Event::Deposit { .. }) => {},
+			RuntimeEvent::Balances(pallet_balances::Event::Issued { .. }) => {},
 		]
 	);
 }

integration-tests/emulated/tests/assets/asset-hub-polkadot/src/tests/teleport.rs

@@ -165,7 +165,7 @@ fn penpal_to_ah_foreign_assets_receiver_assertions(t: ParaToSystemParaTest) {
 				owner: *owner == t.receiver.account_id,
 				amount: *amount == expected_foreign_asset_amount,
 			},
-			RuntimeEvent::Balances(pallet_balances::Event::Deposit { .. }) => {},
+			RuntimeEvent::Balances(pallet_balances::Event::Issued { .. }) => {},
 		]
 	);
 }

system-parachains/asset-hubs/asset-hub-polkadot/src/lib.rs

@@ -1811,11 +1811,11 @@ mod tests {
 	/// Weight is being charged for both dimensions.
 	#[test]
 	fn weight_charged_for_both_components() {
-		let fee: Balance = fee::WeightToFee::weight_to_fee(&Weight::from_parts(10_000, 0));
+		let fee: Balance = fee::WeightToFee::weight_to_fee(&Weight::from_parts(20_000, 0));
 		assert!(!fee.is_zero(), "Charges for ref time");
 
-		let fee: Balance = fee::WeightToFee::weight_to_fee(&Weight::from_parts(0, 10_000));
-		assert_eq!(fee, CENTS, "10kb maps to CENT");
+		let fee: Balance = fee::WeightToFee::weight_to_fee(&Weight::from_parts(0, 20_000));
+		assert_eq!(fee, CENTS, "20kb maps to CENT");
 	}
 
 	/// Filling up a block by proof size is at most 30 times more expensive than ref time.
@@ -1836,10 +1836,10 @@ mod tests {
 	}
 
 	#[test]
-	fn test_transasction_byte_fee_is_one_tenth_of_relay() {
+	fn test_transasction_byte_fee_is_one_twentieth_of_relay() {
 		let relay_tbf = polkadot_runtime_constants::fee::TRANSACTION_BYTE_FEE;
 		let parachain_tbf = TransactionByteFee::get();
-		assert_eq!(relay_tbf / 10, parachain_tbf);
+		assert_eq!(relay_tbf / 20, parachain_tbf);
 	}
 
 	#[test]

system-parachains/bridge-hubs/bridge-hub-polkadot/primitives/src/lib.rs

@@ -90,15 +90,15 @@ frame_support::parameter_types! {
 	/// The XCM fee that is paid for executing XCM program (with `ExportMessage` instruction) at the Polkadot
 	/// BridgeHub.
 	/// (initially was calculated by test `BridgeHubPolkadot::can_calculate_weight_for_paid_export_message_with_reserve_transfer` + `33%`)
-	pub const BridgeHubPolkadotBaseXcmFeeInDots: Balance = 177_594_900;
+	pub const BridgeHubPolkadotBaseXcmFeeInDots: Balance = 88_797_450;
 
 	/// Transaction fee that is paid at the Polkadot BridgeHub for delivering single inbound message.
 	/// (initially was calculated by test `BridgeHubPolkadot::can_calculate_fee_for_standalone_message_delivery_transaction` + `33%`)
-	pub const BridgeHubPolkadotBaseDeliveryFeeInDots: Balance = 942_248_365;
+	pub const BridgeHubPolkadotBaseDeliveryFeeInDots: Balance = 471_124_182;
 
 	/// Transaction fee that is paid at the Polkadot BridgeHub for delivering single outbound message confirmation.
 	/// (initially was calculated by test `BridgeHubPolkadot::can_calculate_fee_for_standalone_message_confirmation_transaction` + `33%`)
-	pub const BridgeHubPolkadotBaseConfirmationFeeInDots: Balance = 172_377_865;
+	pub const BridgeHubPolkadotBaseConfirmationFeeInDots: Balance = 86_188_932;
 }
 
 /// Compute the total estimated fee that needs to be paid in DOTs by the sender when sending

system-parachains/bridge-hubs/bridge-hub-polkadot/src/lib.rs

@@ -1281,9 +1281,9 @@ mod tests {
 	use super::*;
 
 	#[test]
-	fn test_transasction_byte_fee_is_one_tenth_of_relay() {
+	fn test_transasction_byte_fee_is_one_twentieth_of_relay() {
 		let relay_tbf = polkadot_runtime_constants::fee::TRANSACTION_BYTE_FEE;
 		let parachain_tbf = TransactionByteFee::get();
-		assert_eq!(relay_tbf / 10, parachain_tbf);
+		assert_eq!(relay_tbf / 20, parachain_tbf);
 	}
 }

system-parachains/collectives/collectives-polkadot/src/lib.rs

@@ -1194,8 +1194,8 @@ fn test_ed_is_one_tenth_of_relay() {
 }
 
 #[test]
-fn test_transasction_byte_fee_is_one_tenth_of_relay() {
+fn test_transasction_byte_fee_is_one_twentieth_of_relay() {
 	let relay_tbf = polkadot_runtime_constants::fee::TRANSACTION_BYTE_FEE;
 	let parachain_tbf = TransactionByteFee::get();
-	assert_eq!(relay_tbf / 10, parachain_tbf);
+	assert_eq!(relay_tbf / 20, parachain_tbf);
 }

system-parachains/constants/src/polkadot.rs

@@ -90,8 +90,8 @@ pub mod fee {
 
 	/// Cost of every transaction byte at Polkadot system parachains.
 	///
-	/// It is the Relay Chain (Polkadot) `TransactionByteFee` / 10.
-	pub const TRANSACTION_BYTE_FEE: Balance = super::currency::MILLICENTS;
+	/// It is the Relay Chain (Polkadot) `TransactionByteFee` / 20.
+	pub const TRANSACTION_BYTE_FEE: Balance = super::currency::MILLICENTS / 2;
 
 	/// Handles converting a weight scalar to a fee value, based on the scale and granularity of the
 	/// node's balance type.
@@ -122,9 +122,9 @@ pub mod fee {
 		type Balance = Balance;
 		fn polynomial() -> WeightToFeeCoefficients<Self::Balance> {
 			// In Polkadot, extrinsic base weight (smallest non-zero weight) is mapped to 1/10 CENT:
-			// The standard system parachain configuration is 1/10 of that, as in 1/100 CENT.
+			// The standard system parachain configuration is 1/20 of that, as in 1/200 CENT.
 			let p = super::currency::CENTS;
-			let q = 100 * Balance::from(ExtrinsicBaseWeight::get().ref_time());
+			let q = 200 * Balance::from(ExtrinsicBaseWeight::get().ref_time());
 
 			smallvec![WeightToFeeCoefficient {
 				degree: 1,
@@ -140,9 +140,9 @@ pub mod fee {
 	impl WeightToFeePolynomial for ProofSizeToFee {
 		type Balance = Balance;
 		fn polynomial() -> WeightToFeeCoefficients<Self::Balance> {
-			// Map 10kb proof to 1 CENT.
+			// Map 20kb proof to 1 CENT.
 			let p = super::currency::CENTS;
-			let q = 10_000;
+			let q = 20_000;
 
 			smallvec![WeightToFeeCoefficient {
 				degree: 1,