ALL THE NUYEN
Seriously, though. It depends in part on how much you their expenses are expected to be, their experience, their risk, and so forth. A starting group should not be earning more than five to seven thousand nuyen each per run. I used to pay fairly generously, though, and for decently experienced characters (or later those who were run by experienced players and who were especially dangerous in using tactics and just being badass runners even with zero karma) I would easily pay in the ten to fifteen-thousand range, and for 100+ karma they were getting ¥20,000+. Bigger the risk, bigger the reward.