Resource bounds and atomic charging
Current Starknet transactions specify STRK-denominated maximum amounts and prices for relevant resource units. The sequencer estimates and charges the actual fee atomically with transaction execution, subject to the authorized bounds. L2 computation, state changes and data availability can contribute to the result.
Use a current wallet estimate and review the maximum authorization. Keep STRK in the submitting account, including when the contract action concerns another token. Historical guidance that described ETH fee payment can be stale after protocol upgrades, so integrations should follow the active transaction version and official fee specification.