The msg.value sent to ArbitrumDepositProcessorL1.sendMessageBatch() from the dispenser is only checked to be at least as large as cost[0] + cost[1]:
However, excess funds are not returned to the user and will remain in the ArbitrumDepositProcessorL1. It would be more sensible to check for strict equality.
This is also the case in the _sendMessage() functions of the Wormhole target dispenser on L2 as well as in the Optimism contracts on both sides; although, those contracts should not accept any ETH in the first place as reported in a separate finding.
