I myself prefer the current location of higher-paying missions. It forces people out of their little bubbles convieniently marked with a "New" in front of the name. If they were at Core systems, I wouldn't at all be surprised to see people rack up ninety hours of gameplay to then buy a battleship. This would also make New York insufferably busy as opposed to rediculously busy.
Now, the other Core systems like New Berlin for instance, those already pay about as much commonly as New York's high-end payments. So if Core system payments were upgraded by, judging by what Asymptotic says, alot - then New York would be paying like, 200K for missions, New Berlin would be paying about 500K or so, and I just really don't think the military/police have that kind of money to throw around for some extra help. Example:
"Go to the mission waypoint and kill... Six Stilletos!"
"Uh oh! More at the next waypoint! Three more Stilletos and two Weapons Platforms that you don't need to kill and are just for defense!"
"WHOO! Thank you. So much. Our military was way overclocked with the non-existant war going on, so we couldn't spare three Valkyres of our several thousand (no doubt) to take out nine Bundschuh. So I present to you... Half a million credits! All for you! Don't even worry about it. Sure, we could have made about fifty ships with this, but you EARNED it." - (Example based in New Berlin)
Whereas 50K is a perfectly reasonable price for a military to give to an intrepid freelancer or a bonus to a normal Naval pilot's salary. The outer-ish worlds like the Omicrons are reasonable as well. The Order has very few pilots, so it will reward highly for help against the hundreds of BHs encroaching on its territory. In addition, a BH mission at say, FP11 will also pay highly because the Hunters are all crazy psycho for those artifacts and will pay highly to eliminate any resistance. Besides that, the BHs are *really* rich, so they have the resources to throw that at you... And they're a private organization, not a military, so that further justifies greater payments. They aren't bound by budgets and the like. The Core wants the artifacts, they will have them. The Core wants some help, they ask, "How much do you require?"