Again, it all depends on what kind of music you're trying to make. If you're copying an existing style, it's not particularly hard. I can make a Drake-like beat in an afternoon - a quick search on Splice will even show me the exact drum sounds to use.
But if you're creating your own sound? That takes effort and experimentation.
Creating a song - easy. Creating music that's distinctively your own - tons and tons of effort.
Also, "tons" is amazingly overstated. Very few of those 16 year olds are producing "good" music that appeals beyond their immediate demographic, and that's to say nothing of how low of standards many youth demographics have.
It probably took me about 10 years to get good at programming. Sure, I could create programs pretty quickly---but making something like [1] is another matter altogether.
I guess it depends on how you count, but not really, at least not for the first 6 years or so. The first two-ish were high school, the next four were college, and the next six were in graduate school (so on a grad student's salary). After that I got a "real" job.
For what it's worth, I do other artistic pursuits as well. I did music for about 15 years though I wouldn't say I was ever good. I've been writing for about 10 years. I would say I'm just now barely at the point where I think I can write half-way decently.
To be clear, I am very aware, and very grateful that one of the things I happen to like doing also pays well. I was responding more to the "you can't imagine the level of effort required to do this work" aspect of the ancestors' comments. Yes, I can imagine, thank you very much. While I don't like where we're going with funding models for art, that doesn't mean that understanding the effort is the limiting factor.
I don't think anyone is disputing that ROI is better with software.
That said, programming for 10 years before getting a job in the are is not uncommon. Most of my peers did it for at least five (I learned 15 years before, but I grant that's not that common).
But if you're creating your own sound? That takes effort and experimentation.
Creating a song - easy. Creating music that's distinctively your own - tons and tons of effort.