A transaction lists a gas limit of 100,000 and gas used of 60,000. Those are not two competing estimates of the same final charge. The limit sets a ceiling on computational units for the transaction; gas used records the work charged during execution.
Ethereum’s gas documentation explains gas as a measure of computational effort and distinguishes the transaction limit from fees per unit. It also explains that a transaction running out of gas during execution can revert its changes while still consuming gas for the work performed.
Keep units and prices in separate columns
In a simplified illustrative calculation, 60,000 units charged at an effective price of 10 gwei per unit produce an execution fee of 600,000 gwei, or 0.0006 ETH. The 100,000-unit limit is not the quantity automatically multiplied into that final execution fee.
This example is arithmetic, not a recommended setting or an estimate for a real transaction. Other transaction types and networks can include additional fee components. Read the receipt and documentation for the network actually used.
Check the outcome as well as the cost
A fee appearing on a receipt does not prove that the intended transfer or contract action succeeded. Check the transaction status and the relevant result. A failed execution can still incur a cost; a rejected request that never entered a block is a different situation.
Do not lower the gas limit at random in an attempt to make a contract interaction cheaper. If the operation needs more computation than the permitted limit, the attempt can fail rather than become a smaller successful version of the same action.
When comparing two receipts, note the network, transaction type, gas used and effective price. A more expensive receipt may reflect a higher price per unit, more work, or both. Comparing only the final ETH number hides that distinction.
Use a read-only explorer view for learning and avoid signing transactions simply to test terminology. Understanding the receipt is a useful first step before deciding whether an unfamiliar contract interaction is necessary or worth its risks.