fix(runtime): price Substrate weight and bytes like EVM gas (50_000 wei per ref_time, 16 gwei per byte) — transfers cost ~1.6e-5 ORB instead of ~3e-10, so account and block spam are no longer free (spec 20)

template/runtime/RUNTIME_VERSIONS.md

@@ -32,7 +32,8 @@ sign through the new `Ed25519Text` (`0x03`) and `Ed25519WrappedText` (`0x04`).
 Circuit keys: unsound ones are recorded on chain and never verify again, a
 removed version keeps its key, and a key without phase 2 is refused.
 Shielded pool: a replaced root stays spendable for a full window, and spends
-creating the same note are exclusive in the pool.
+creating the same note are exclusive in the pool. Substrate fees price weight
+and bytes like EVM gas.
 `transaction_version` is unchanged. Ships with `pallet-evm-precompile-balances`
 0.2.0, `pallet-zk-verifier` 0.19.0, `orbinum-zk-verifier` 3.4.0 and
 `pallet-shielded-pool` 0.25.2.
@@ -140,6 +141,17 @@ creating the same note are exclusive in the pool.
   change note each `provide` a pool tag, besides the spent nullifiers: two
   spends creating the same note can no longer both sit in the pool and
   propagate when only one can execute.
+- **Substrate fees aligned with EVM gas.** `WeightToFee` was `IdentityFee`,
+  1 wei per unit of `ref_time`, so a transfer cost about 3e-10 ORB: a million
+  new accounts cost 0.0003 ORB and filling every block for a day about 0.03 ORB.
+  A unit of `ref_time` now costs the default base fee over `WeightPerGas`
+  (1 gwei / 20_000 = 50_000 wei) and a byte 16 gas (16 gwei), so an extrinsic
+  costs what the same weight costs as EVM gas: a transfer about 1.6e-5 ORB, as
+  over EVM. `ExistentialDeposit` stays 0: above it, an EVM account emptied by a
+  Substrate transfer is reaped, its nonce returns to 0 and its earlier signed
+  transactions can be replayed, and the shielded pool's account could burn the
+  remainder backing pending fees. Unsigned spends (`MinSpendFee`) and Root calls
+  are unchanged.
 
 ### spec 19 — tx 7 — 2026-10-13 (`v0.5.0`)
 

template/runtime/src/configs/system.rs

@@ -81,11 +81,22 @@ impl pallet_balances::Config for Runtime {
 	type DoneSlashHandler = ();
 }
 
+parameter_types! {
+	/// Fee per unit of `ref_time`: what the same weight costs as EVM gas at the
+	/// default base fee (1 gwei / 20_000 weight per gas = 50_000 wei). A
+	/// Substrate extrinsic costs what the equivalent EVM transaction does,
+	/// instead of 1 wei per unit, which made accounts and blocks nearly free.
+	pub WeightFee: Balance = (DefaultBaseFeePerGas::get()
+		/ U256::from(WeightPerGas::get().ref_time())).low_u128();
+	/// Fee per encoded byte: EVM calldata's 16 gas per non-zero byte.
+	pub LengthFee: Balance = (DefaultBaseFeePerGas::get() * U256::from(16)).low_u128();
+}
+
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type OnChargeTransaction = FungibleAdapter<Balances, ()>;
-	type WeightToFee = IdentityFee<Balance>;
-	type LengthToFee = IdentityFee<Balance>;
+	type WeightToFee = ConstantMultiplier<Balance, WeightFee>;
+	type LengthToFee = ConstantMultiplier<Balance, LengthFee>;
 	/// Parameterized slow adjusting fee updated based on
 	/// <https://research.web3.foundation/Polkadot/overview/token-economics#2-slow-adjusting-mechanism>
 	type FeeMultiplierUpdate = SlowAdjustingFeeUpdate<Runtime>;

template/runtime/src/lib.rs

@@ -38,7 +38,7 @@ use frame_support::{
 	genesis_builder_helper::build_state,
 	parameter_types,
 	traits::{ConstBool, ConstU32, ConstU64, ConstU8, OnFinalize, OnTimestampSet},
-	weights::{constants::WEIGHT_REF_TIME_PER_MILLIS, IdentityFee, Weight},
+	weights::{constants::WEIGHT_REF_TIME_PER_MILLIS, ConstantMultiplier, Weight},
 	PalletId,
 };
 use pallet_ethereum::{Call::transact, PostLogContent, Transaction as EthereumTransaction};

template/runtime/src/runtime_tests/weights.rs

@@ -8,3 +8,20 @@ fn configured_base_extrinsic_weight_is_evm_compatible() {
 		.base_extrinsic;
 	assert!(base_extrinsic.ref_time() <= min_ethereum_transaction_weight.ref_time());
 }
+
+/// Substrate fees price weight and bytes like EVM gas at the default base fee:
+/// the weight of 21_000 gas costs what 21_000 gas does.
+#[test]
+fn substrate_fees_match_evm_gas() {
+	use frame_support::weights::WeightToFee as _;
+
+	let base_fee = crate::DefaultBaseFeePerGas::get().low_u128();
+	assert_eq!(crate::WeightFee::get(), 50_000);
+	assert_eq!(crate::LengthFee::get(), 16 * base_fee);
+
+	let transfer = WeightPerGas::get() * 21_000;
+	assert_eq!(
+		<Runtime as pallet_transaction_payment::Config>::WeightToFee::weight_to_fee(&transfer),
+		21_000 * base_fee
+	);
+}