Let me start with two pieces of unrelated information.
Random fact number one: I'm a fan of cable-free environments, and specially when it comes to my house. I have a computer screen, speakers, a PS3 and a laptop all connected together, with no cables lying around. This presented a challenge, though, because the speakers only have one 3.5mm input (as in, the same one your headphones use) and I wanted to plug two things at the same time. The PS3 has an RCA adapter, while a male-male cable can be used for the computer (that I plug into the headphones socket). So here I have three male connectors that I need to connect together, ideally without any intervention afterwards (I don't want to plug and unplug things all the time).
Random fact number two: there's a German company which I've seen in the Mauerpark Flea Market selling something they call Pokket Mixer. This is a mixer reduced to its simplest shape, in which you plug two devices through its headphones and get one single output. It costs €90 (okay, € 89,95), and looks fairly nice.
Now, you would thing that this two pieces of information complement each other perfectly, right? Get a mixer, plug both sound inputs, and problem solved. But alas, that's not the case - I cannot justify spending that much for something that, let's face it, is more a result of lazyness than anything else. So I looked for alternatives, and lucky me, I found this simple stereo mixer that does the same thing, but with less features and is a lot cheaper. I built one of those for around € 10, and now I'm happy.
Then, an idea crossed my mind: I could add a sound control to this thing. It would still be under € 10 (let's say € 20 for the really fancy options), and I could sell it for € 60. As I'd do it as a hobby and I already have a job, I can sell it at a lot less than the other guys, and still make some easy income on the way. By not having to pay any bills nor worrying about the sustainability of my project, my definition of success is fairly reachable.
But then again, there's only so much market for pocket mixers. After all, is not the kind of thing you buy over and over. Being significantly cheaper, my project is likely to be good enough for the casual listener, so I could have a chance at capturing that market, but that niche is bound to dry up eventually. And then again, when that happens I can just sell my stock at a discount and go back to my regular job, but how about the guys who actually are making a living out of it? Is it fair for me to make their business harder just because I'd like to buy more comics per week? I know the free market is all about competition and taking every chance, but is it ethical for me to do that?
So, as you can see, I'm more worried about the consequences of my success than the consequences of my project being a dud. It is clear to me now that I'll never be rich, because in order to do so I'd have to want money for the money itself, and I just can't do it. I don't want to be the kind of person that leads a market, simply because that would require me to crush the competition, and I can't bring myself to crush someone's job just for the sake of money, not even hypotetically.
Not that I'm complaining. I just wanted to point it out.