Shadowrun 5th has gone a long way towards explaining risk vs reward when it comes to paying out for jobs. Without giving out too many specifics it works out to be around 4-5K per runner per session with the option to adjust things here and there in the form of phat lewtz.
Its also a Shadowrun trope that the Johnson/Fixer always lowballs payment. I used to work for a company that had an electric gate that would at the push of a button slide open. Every two weeks the gate would break and I was one of the people that had to go out there with a fork lift and pull it open. I asked the boss, "I know it costs money to have people come fix this gate every few weeks, but do you think maybe they're not doing their best so they'll be paid every two weeks or so to fix the gate again?"
Mr. Johnson has a slush fund for hiring a team, if he can get them cheaper that's good for the company. A fixer is offered a stack of cash and if he can lowball a team to do the job cheaper. Well he just pockets the extra. Its how things work. So its expected that player characters will negotiate to get more cash for the team.
Negotiation is give and take. Its also usually handled with a simple formula of raising/lowering the payout by +/- the net hits in the Negotiation roll * 100-500 nuyen. With those sneaky behind the screen things this allows the GM to give the runners extra up-front cash without unbalancing a campaign. The min/maxed Face that likes to pre-spend Edge to blow past limits then throw 25 social dice? Not a problem, his hits are only worth a hundred each. That guy out of town this session and the technomancer has to default her charisma for negotiation? Welll maybe her hits are worth 500 each this week.
This give and take style of negotiation breaks down when the players handle negotiation in hard numbers. The Johnson offers three thousand each for a job. The runners demand eight thousand each. It puts the GM in the position of saying, "Well okay either I pay them somewhere in the middle...which is more than I am comfortable in giving them, or this is going to be a really...really short session."
If the GM gives in and says, "Well okay, the Johnson is willing to give you each six thousand for the data steal job," it sets the bar for data steal jobs at six thousand. After all if the job is basically the same, with roughly the same difficulties. Tom the Mr. Johnson paid us six each, and Bob the Mr. Johnson will only do four? What the hell?
The GM has gone from a progression of three thousand per data steal job to six thousand per job. Top that off with the fact that Mr. Johnson/The Fixer always lowballs the payout. "He's offering us six thousand for the job, that seems kinda low. I want to roll negotiation."
In closing, when handling a negotiation try not to set hard numbers down on the table. It gives the GM a lot less "wiggle room" for keeping control over game balance. Shadowrun is often a stuff based game. You get paid karma/cash and you spend it on goodies you want. If within a few sessions you have milspec armor 0.005 Essence in Delta grade cyber while rocking a tricked out deck where do you go from there?
I guess the only place to go is start building your own mass drivers so you can Thor Shot dragons.