@nomicfoundation/ethereumjs-tx/src/capabilities/eip1559.ts

Implementation of the various Ethereum Transaction Types

import type { EIP1559CompatibleTx } from '../types.js'

export function getUpfrontCost(tx: EIP1559CompatibleTx, baseFee: bigint): bigint {
  const prio = tx.maxPriorityFeePerGas
  const maxBase = tx.maxFeePerGas - baseFee
  const inclusionFeePerGas = prio < maxBase ? prio : maxBase
  const gasPrice = inclusionFeePerGas + baseFee
  return tx.gasLimit * gasPrice + tx.value
}