Gas fees are payments made by users to compensate for the computing energy required to process and validate transactions on the Ethereum blockchain. ... A higher gas limit means that you must do more work to execute a transaction using ETH or a smart contract.

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Gas can get expensive when the Ethereum network is experiencing a high volume of transactions. For each new block added to the Ethereum blockchain, there is limited space for how many transactions can be included. Due to supply and demand, miners are incentivized to accept transactions at higher gas fees.