I could be misunderstanding how the baggage scanners work, so please correct me if I’m wrong. However, it seems like once you get to the level 3 scanner, it’s the most accurate of the bunch. So, doesn’t that make the level 1 and 2 irrelevant? There should be a cost to using the level 2 scanners, and an even higher cost to use the level 3. That cost could be actual money, time, or both.
My suggestion is that maybe the level 1 scanner is free to scan each bag and is the fastest scanner. Then, the level 2 scanners cost money per bag scanned (operating cost), and also take longer to scan each bag so it has the potential to back up your baggage scanning line, which encourages you to keep the level 1 scanner. Then, the level 3 scanner has an even higher monetary cost per bad scanned and takes an even longer time to scan each bag (since it’s a human scanning the bag), which encourages you to keep the level 1 and 2 to lower your per bag scanning cost and prevent your conveyor belt from being backed up.
Currently, (unless I’m missing something), once you get the level 3 scanner, you don’t really need to level 1 or 2 scanners since it is the most accurate (according to the description) and doesn’t really cost more per bag (just the hourly cost of the security agent) and is just as fast as the level 1 and 2.