Hey Radan, can you please try to refrain from using any parenthesis? It seems like you're interrupting yourself and makes reading your thoughts more difficult then it should be. On to the topic at hand, however:
The Gigs: A gig is a job taking place off screen. All of the barter made from these gigs are the Operators do do with whatever he pleases. If the NPC crew, or the players, start to feel like they are being taken advantage of... then play it out. How much barter should the Operator pay his crew? Well, how much do they want? How much are they worth? How much are they making? How many jobs does the crew know about, are there any that are happening off books? Is the crew making enough barter to hit the monthly cost of living? Do they have other problems that go beyond what they can handle on their own?
The reason the rules leaves this situation vague is because there are hundreds of different things which could change the result of the move.
Alternative perspective: As an MC, you have the right to say that the NPCs that are part of the crew don't need to be given barter. It can assumed that the 1-barter profit from the gig is your share of the loot from the job. If you want to have the crew need more barter for something, make an event out of it. The book does say that the crew shouldn't be entirely free, however, so maybe every now and then they have to come up to the Operator and introduce a problem they've gotten themselves into, or that has befallen someone they care about who has no barter to pay them. Maybe that problem is going to take some work, cost some money, etc. If the Operator does this and helps them out, then they have a happy and more loyal crew. If they leave them hanging in their times of needs, maybe they've made an enemy that feels like the Operator set them up to fail. Do what the fiction demands.
If they are PCs then DO NOT give them additional barter for it. This is a moonlighting roll, happening off-screen. If the Gunlugger is part of the crew, then the Operator knows he'll have to pay him for his help. When players are involved, make sure they all have good reasons to be involved. They don't need to help each other just because. The limited barter from each job will promote each character doing their own moonlighting. Maybe the Operator has to do something else for the player crews on screen. Let the players figure that out, but I will reiterate: Don't create more barter from the gig just because another player was part of it. Let them solve the cut out themselves.
The cost of barter: Keep in mind, that when you have an event that triggers a cost, be that suffering harm, needing specific gear, makes an enemy; you have a situation that might cost some barter to resolve. You literally have any number of ways to handle the "cost" of maintaining the crew, and just as you mentioned before, barter could be any number of things including a service that was hard to get.
Number of Gigs per barter: The easiest way to determine this is quite simply, if your operator is overflowing in barter, then trigger events that make that barter come into play, move, and create the fiction. So if the Operator has something like four or five barter on hand, maybe you decide that it's time that he has to put that barter to use. Trigger an event from his crew that might cost him something, or that needs barter to solve. That doesn't limit you to bribery either, it might cover the cost of the life saving medicine/information/tech from another hard-hold/character/gang for the crew members kid/mate/other loved object. You are only limited by your own creativity. How much is too much, you ask? I don't know, in your fiction, how much is too much?
Doing Murders: An Operator has the ability to get a load of barter for this move, sure, but at the same time... You are welcomed to complicate his life for doing so. Maybe he doesn't do it secretively? Maybe everyone knows about it, maybe their friends, allies, etc take issue with it. Maybe it closes off his connections to someone else. Its not so much that he makes more money then the gunlugger for the same thing, the gunlugger does his on stage and full blown action movies. The Operator might simply be using his connections to get paid three times from different clients for the same murder. Maybe all this killing off-screen comes back to bite him in the ass on screen. The gunlugger is a god-damned-bad-ass and a walking-death-machine. They'll be a lot less vulnerable to revenge then an Operator. It's your job to make the world seem real. If they're earning that much jingle, it means that the gig comes with that much risk to him after the deed is done.
The Maestro'D: If they are doing an event everyday all the time, then it'll probably cost a barter every day they keep it up. 12 hours during the day, 12 hours during the night. You can bet they're paying a revolving staff for the job. But this again is something you need to be smart and willing enough to decide for yourself. A spectacular event isn't the norm, it should not be something you allow to be sustainable, it should cost him something to do, but matter for the fiction when it happens. One spectacular event lasting a week? maybe, but a 24/7 event lasting a week, longer? Probably not. Decide for yourself. The suggestions and wording on the pages DO NOT overrule your job as an MC to make the world seem real, and the allowing them to use a barter to break that reality is just a bad move on your part. There are no tricks, deceptions, or loop-holes within AW. If you think you've found one, stop right there, and THINK. Because I bet you you could figure out a way to read the same thing in a way that doesn't break the fiction.