Sure, not all jobs are created equal. But there are a million variables here: when the job is created, the salary, whether it's filled by a current resident or a newcomer, how much public infrastructure the worker uses, etc.

More to the point, though, the goal of the city isn't to maximize its revenue — it's to make its citizens lives better. A minimum wage job for a poor current resident might be better the community than high-paying job for an imported knowledge worker, even if the latter means more money for the city.