Always remember that `address(this).balance` includes also `msg.value` of the current transaction.

Unreachable.sol

// SPDX-License-Identifier: WTFPL
pragma solidity ^0.8.19;

contract TryToReachMe {
    constructor() payable {
        assert(msg.value == 1 wei);
    }

    function tryMeBabe(address addr) public payable {
        uint256 balance = address(this).balance;
        if (msg.value > balance) {
            unchecked {
                payable(addr).transfer(balance + msg.value);
            }
        }
    }
}