Firstly, 50-Cent versus Brain Surgeons is actually a very simple one: there are many brain surgeons (not a ton, but many) and only one 50-Cent. Also one is a performer, which is something inherently unique. Despite the KPop industry's assertions, you cannot "train" a performer. Brain Surgeon on the other hand is a job you train for; it's a lot of training, at great expense, but it is still training and there are many: 33,000 worldwide according to Google. So that's just simple scarcity.
Secondly, there is a massive flaw here that I can't quite put into words, so I'll attempt to show my reasoning for what I'm getting at:
* Workers are paid for (in a perfect world) by the profits of a business that generates revenue providing a service. Therefore, whatever that service generates in revenue is passed to employees in whatever structure. By extension of the above, the rarer a service is by whatever measure be it difficulty, hazard, required equipment, regulation, training, etc. the more expensive that service is and therefore the higher paying that job should be. This is why neurosurgeons make more than McDonalds cooks.
* Cafeteria chefs, short order cooks, waitstaff, baristas, etc. are all examples of jobs that are almost universally terrible, universally poorly paid, and absolutely essential to many people's daily lives. They may not generate very much value individually, but if tomorrow they all decided to fuck off and not come to work, society as a whole would notice and be definitely worse off for it. In addition, to large groups of the population such jobs are their only source of income. We therefore have a situation where many entire sectors of the economy are composed of jobs that do not pay their workers enough to live, yet we absolutely need them. This doesn't make sense and is not sustainable.
What I'm saying is: you cannot have a situation where someone's still essential job does not pay them enough to live. Eventually, something has to give: we have to accept that just because someone lives a life of simple labor that they are not ours to then condemn to a life of check-to-check stress, lack of healthcare, and poor living conditions, especially when the majority of those in that life did not choose it, because who the fuck would choose that, but were forced into it by circumstance, fortune, poor decisions early in life, or some combination of the three.
Now, how we solve this problem I'm not remotely qualified to say. Basic Income is one idea, raising minimum wage is another, both of which will have far reaching implications that I can't even get into right now. What I'm saying is: the current scenario is not morally right, and not economically sustainable. We need something different.