"If great speakers are being made, then the knowledge exist, so why don't all producers make great speakers. What makes a speaker great, and how much does it cost to make one?"
Rok2id, that's a fair question. The answer, I think, isn't any different than the reason why not every composer writes a great symphony, despite the fact that music theory and training are available to all. Speaker design isn't nearly as cut and dry and scientific as you think it is. Yes, it's highly technical -- but then, so is music.
Suppose you were a speaker designer. Assume that you learned everything you could about physics, acoustics, loudspeaker design, and psychoacoustics. You'd be amazed at how much you knew -- and how much you still wouldn't understand, because we don't yet know.
Then, try designing your product. You'll rapidly find yourself coming up against what are known as the engineering trades. The materials you use are imperfect. Each has its own strengths and weaknesses, so when you gain one thing, you give another thing up.
You might for example choose to make an electrostatic speaker. Electrostatics are famous for detail and low distortion. But because of fundamental and practical limitations, they have to be very, very big to play low and loud, and it's hard to get good high frequency dispersion out of them. They're also hard to drive and tend to be unreliable.
A great designer will study what's known, then add some problem-solving innovations of his own, maybe even come up with an entirely new approach. He'll spend years mastering the "black art" aspects of speaker design that aren't in the textbooks, things that you learn only by spending hours in the lab tinkering with prototypes, listening, measuring, and trying to make them better.
So, while you can indeed design a good speaker by the book, using off-the-shelf parts, designing a great one at a practical price point isn't at all cut and dry.
Add to this the fact that the rule in consumer electronics is that a product has to retail for 4-5 times parts and labor cost. As with most things, you can buy a lot of performance. A machined aluminum cabinet costs a lot more than an MDF cabinet, for example, but it has fewer of the resonances that give speakers a boxy, smeared coloration. Exotic diaphragm materials, large multiple woofers for low distortion and high power handling, etc. -- all of these are costly.
Anyway, just trying to give you a sense for why this isn't nearly as trivial as you might think. And it also helps explain (along with what might politely be called commercial considerations) why there isn't a simple relationship between price and greatness in a speaker.
A pair of Quads, for example, will cost only $10,000 and are unquestionably great speakers if they fit your listening needs (limited SPL and bass). There are also great speakers that cost over $100,000. They excel in different areas, because of characteristics in the underlying technology.
Bottom line, I think, is that you should as others have suggested try to listen more. Not because you should become an audio hobbyist, but because you'd be amazed at what they can add to the enjoyment of music. If they take your breath away, then you know.
