Kreisler, there's nothing to disagree with in your first couple of sentences, and I'm sure major composers' works subsidize new work, but I have another view of what's going on. Publisher's income is in two parts, score sales then performing rights on the works. It's in a publisher's interest to have a known contemporary composer's works in their stable especially if they're getting performed in prestigious venues. The performance aspect is probably going to subsidize the score production. I would imagine that they don't even care if the score sales operate at a loss - it's made up for many times over on the performing rights.
I think you are right. And if you go to the major publishing houses' websites (those that actually do publish new music - the ones specializing in urtext editions generally don't), you will usually find some sort of "composer" listing that will produce the names of many living or recently living composers, some of whom will have piano music available.
Of course, many composers are self-publishing these days. Finding them requires different methods. There are various websites that are devoted to new music that can helpful, such as NewMusicBox
. Another way is to pay attention to the repertoire of the many pianists who play new music. They all have websites, so it's easy enough to explore, and, like most stuff on the web, one thing leads to another.