Good music doesn't need to be marketed.
Setting aside all the royalty and production costs--which are more complex than it appears you believe them to be--this is the single most wrong statement I've read in a long while. You think people automatically know when something of quality exists? There are only a few ways of introducing anyone to music:
1) Radio play. And if you don't think it costs record labels quite a lot of money to get their artists's songs pushed into heavy rotation, then you haven't been paying any attention to the industry at all. Even outside of the illegal payola operations--which have been rampant by most accounts--the labels have to make radio programmers aware of, and capable of, playing a song for it to even make to the airwaves.
2) Music videos. These are increasingly expensive, because each time out it seems that someone has upped the ante on what a music video can or should include. Long gone are the simple days of an artist lip-syncing with some choreographed back-up dancers. And even once you've spent the money to produce the video, how does anyone know it's out there to see it? Music video channels have all but abandoned playing music videos, and that only leaves the Internet. Exposure on artist and label websites costs money, and you better believe that Amazon, iTunes and other e-retailers collect a handsome fee to prominently feature anything on their sites.
3) Singles, either for airplay or sale (mostly digital these days), and they adhere to the same conditions as music videos.
If you think it's "cheap" to produce a song, much less an album, and then get it out to the public, then I have to believe you haven't done your homework. Even if you forgo studio time and record using computer software at home, you've got to record in a music-friendly environment and that means sound-proofing a room. Unless you're an acoustic-based folk singer, there are various instruments to be recorded, back-up singers, etc. to be added to the tracks. Those performers charge money, especially the really good ones who can come in and nail their parts without wasting a lot of expensive time.
Here's an easy experiment. Whatever genre you like, go to Billboard.com and look at the top chart for the week. You'll be familiar with the artists that keep getting regular play. Take a look at the record label for each of the top songs/albums. Most of the labels have one, maybe two, A-list artists that keep getting out there, then they sort of rotate through a handful of others who may or may not have something new to promote at any given time. For Big Machine Records, their A-lister is Taylor Swift, hands down. Nobody else on that label gets the airtime and exposure she gets, and it's not because she's so good she doesn't need marketing. Elvis needed marketing, too, and that's why he hired Col. Parker.
Don't assume that just because you have an image of every newcomer rolling in bathtubs of $100 bills with thirty strippers drenched in Dom Perignon that the music industry is some kind of get-rich-quick-and-get-richer operation. The truth is that most of the artists and songs that a record label takes a chance on wind up costing them more money than they take in.