OP, you are absolutely right in one limited sense. On average, students of STEM fields can expect to earn more money over their lifetimes than non-STEM graduates. I am however surprised that your obviously bright and logical mind tripped over one or two things when you raced to the conclusion of your argument (which doesn't follow necessarily from the premises).
Firstly, you wrongly conflate 'better in some sense I find preferable' with 'objectively superior'. That's a dangerous claim for a scientist and I hope they beat that mentality out of you at University. Whilst you may believe that raw earnings is simply 'better', may I point out that the overwhelming number of people in positions of power in government have non-STEM degrees? For many years I have heard the lamentations of my (fellow) Engineers about 'non-technical' management having power over them, but it is a general fact across most industries. Marketers, designers, HR, these people are overwhelmingly non-STEM and they get to decide the direction of things, especially in my industry (tech). You say you want to go into finance? Good luck acquiring any creative satisfaction from moving money around. Many people for example accept the life of the artist (as an example), poor and thankless as it may be at times, because they attach some higher value to creating or performing. You want to enter finance, so you should probably understand the price you have to pay, like so many others, in your narrow and dogmatic pursuit of money: autonomy, creative satisfaction, free time, vastly increased risk of suicide, alienation from others due to a highly competitive work environment and likeability amongst the general populace to name a few.
I should also point out that, particularly in the US, former STEM majors often relentlessly chase the 'struggling artist' and other non-STEMs from city to city, as STEM is generally unable to produce one of the most valuable things to human life: culture, which is itself more necessary than a hedge fund. So the next time you believe what you're doing is more valuable, look up the historical contexts of gentrification.
Second, the term 'average' here is pretty important. Average earnings are higher for STEM grads over their lifetimes (although social scientists for example basically even it out once they hit around 30 and enter management roles). It is true that many people aren't able to turn what they know into a sufficiently valuable commodity, but the most public figures of note are either non-stem grads, or don't actively do stem work in the stuff that made them public figures of note. You may think that all those music students who became DJs who made it big, politics students who got into positions to influence policy, sociologists who write for big magazines don't do anything as cool as you do, but I promise you they earn a LOT more money.. A specific cohort of non-STEM grads tends to beat the absolute crap of STEM grads, both in terms of fame and fortune because culture is a very valuable commodity. Many people bank on being that exception, and they take that risk, most fail, but some succeed. Personally, I'd rather take that shot (and I did) and I've been successful. How? I got a non-STEM degree, taught myself computer programming and built my own portfolio of software, and now I am paid far more because I have skills that the STEM grads (who know far more in terms of real coding) don't. I can handle the design and most of the engineering by myself, managing both teams, I am trusted with client-facing deals, and I also have a sharp eye on a marketing strategy outline AS I am building the product. Breadth, in some cases, is just as valuable, if not more than depth when it comes to actually leading people.
The third and final point is that you want to work in finance. Let me tell you, as somebody who studied Economics at University, that I don't think you have ANY claim to believing your chosen studies above and beyond the likes of 'sociology'. Economics is literally the psychology and sociology of human beings under conditions of scarcity. That is it. Economics is split into something like 11 different major schools all with widely varying conceptions of these factors, and they construct abstractions and models that produce extremely general predictions. Careful which school you find yourself believing in though, because if you actually have an ounce of intellectual curiosity about the subject you'll pursue your studies by looking at the entire spectrum, but you better pick the one the IB's want so you can get your fat paycheque right?
I'll finish with a question. Do you want to go to University to learn new things, or to get a piece of paper to say that you can earn XYZ salary? Genuinely curious. (And just in case you say both, which is more important to you?)