I guess it really depends on the target, the time frame, and how much you care about the likelihood of success. There are people in real life who hire "hitmen" on Craigslist to go murder people. Often it turns out to be an FBI agent in disguise, but sometimes it's actually a person willing to go shoot somebody. I've seen news reports where the prices on this can be dirt cheap, like a hundred bucks. I don't think that money would get you somebody competent, but what do you expect for that much?
So let's say that you are Count Vlad von Schemer. Major Victory and the Hero Battalion have been a thorn in your side for too long. You want to put a bounty on his head, but you don't want to spend a lot of money. What kind of results can you expect from each price tier? (This isn't necessarily how much you're offering, but how much you're spending)
100 C-bills or less: A guy who lives in a trailer park near the merc base will agree to go to Major Victory's house, kick in the door, and shoot him. He'll probably be high when he does it, and he may or may not remember to wear a mask. Likelihood of success: less than 1%. He'll almost assuredly be caught, probably before he even gets on the base. But the good news is, you aren't out a lot of money. You could hire guys like this all day.
1,000 C-bills: You could put a whole team of trailer park guys together. Get them a cheap van, and the next time Major Victory is out in public, they'll drive up next to him, yank him into the van, and drive off. Or they can shoot him if you like that better. Likelihood of success: 1%. In all probability, Major Victory is armed, and these guys are just gonna get shot. Total amateur hour here.
5,000 C-bills: Now you're talking a nice chunk of change for a normal person. You might actually get a mob or cartel enforcer or two with this kind of money. They have experience with this sort of job, but generally not on such a well defended target. If Major Victory has a coke habit or something, or maybe he likes the hookers, you might be able to catch him off guard. Wait until he goes up to the hotel room with the sultry redhead you sent down, and then Vinny and Tony club him in the back of the head. Likelihood of success: completely depends on target. Could be pretty good if everything goes right. If you've previously had a failed attempt, odds are very low because he'll be on his guard. If he has no easy to abuse character flaws, odds are even lower. This is the first level where it might actually work though. If he has the right character traits, maybe 30%?
25,000 C-bills: At this point you could probably hire a small team of professionals. We aren't talking crack military experts, we're talking basic regular infantry. You might get a squad of foot infantry from a nearby merc unit who are willing to take a side job. This is well above normal rates to hire infantry, particularly since it's one night's work, but they're also subject to far more risk since they're guaranteed to engage the enemy and they have no backup. I'm presuming a nighttime raid on Major Victory's base, sneaking in, grabbing him, and sneaking out. Likelihood of success: 10%. For this price, you aren't really getting the guys with the right skills. They're probably gonna trip an alarm and get into a firefight. If they were really good enough to do this, they'd charge a lot more, so you're really getting guys who think they're better than they really are (and so they're bad at calculating the odds).
100,000 C-bills and up: Now you start being able to pay off multiple people so that your odds of success go up. The astech working for the Hero Battalion who has a lot of gambling debts, maybe he has to shut off the security system for a few minutes to rewire something. A security guard who feels like he missed his shot at the big time, maybe a few grand in his pocket will convince him to deliver a package, or wave in a delivery truck at the checkpoint. I'd say this is the first level where you can have some reasonable chance of success.
Million C-bills and up (way, way up): This is when you can start getting battlefield units to intentionally target Major Victory. Maybe a lance of Jenners comes in during a battle and tries to cut his mech out from under him. But he's probably going to be in a really tough mech, and they'll get all his attention. A single lost mech is very expensive, and you're sending them into a meat grinder, guaranteed. They're going to charge a lot for this.
Note that all this is still super dangerous. If the Hero Battalion finds out what you're doing, you've got an entire battalion coming down on you. They've got a lot of resources, and they can hire assassins too.