That's exactly why I still use SR3's Money-for-Karma and Karma-for-Money rules. That way, as a GM I can hand out karma and nuyen at normal rates and let the
players be the ones to handle the bugeting of their resources.
I tend to give out about 5 karma and 7,500 nuyen per run (on average) over the early stages of a runner's career (that is, below the 100 karma mark). That means, in roughly 20 runs any given character will have 150,000 nuyen in earnings when they reach the 100 karma mark. This is
not nearly enough money to keep a cyber monster happily upgraded, but more than enough karma to let them learn virtually every skill they want and increase said skills to reasonable levels. Likewise, 150,000 nuyen is a virtual fortune to a magiker, but 100 karma is just a tiny drop in the bucket compared to their karma needs.
With this amount of income (in both karma and money), both general character types have enough income to upgrade a bit, but no where
near what they need to be truly competative. Remember, all this time the opposition is getting tougher and more insane, and most of the time the opposition has an unlimited budget.
So, when the 100 karma point in the campaign rolls around, the players still want
more. While marginally satisfied that they've been able to upgrade a bit and save a bit of money, they still often feel desperate to get that little bit more karma/ nuyen that'll let them Initiate again/learn that new spell/afford that piece of beta-to-delta grade 'ware that they feel they
need to stay one step ahead. That's where the Karma-to-Money rules come in, allowing the character to trade off what they don't need (as much) for what they do (desparately) need. This makes the players happier, but also has the side-effect of draining their resources which leaves them needing more money/karma. Which means they go on more runs, facing tougher and tougher opposition/problems and making more enemies that they
need to upgrade to cope with, which leads them back to the same dilemma.
The net effect of this is that it leaves the players always
hungry for more, and it works like a charm. In 15 years of playing and GMing SR, I've never had a "campaign" end due to lack of interest and only seen a grand total of 4 characters actually retire.