Ah, that's an excellent question, and I do have a related theory, though I cannot substantiate it with hard-and-fast data, and I'll say nothing about Sabian, as I have little direct experience with their products. Nevertheless, here's the gist: Paiste has been making non-B20 sheet cymbals and promoting them as professional grade for a very long time, so Paiste disciples have no opposition to such composition or mode of production. Paiste, therefore, can charge top dollar for non-B20 offerings, and its adherents won't blink an eye. The Zildjian consumer, on the contrary, clings largely to the delusion that non-cast, non-B20 cymbals are categorically substandard. Hence, it's improbable that long-time players of As and Ks will convert to Ss (B12), and it's equally unlikely that Paiste lovers will flock to Zildjian. What's Zildjian's response? Lower the price range of non-B20 offerings, and newcomers -- those devoted to no manufacturer -- will swarm the stock like flies. It's a rather brilliant scheme that I trust is paying dividends for Zildjian.
Let us examine, in cursory fashion, why Ks, for instance, cost more than Ss. It's not that Ks are materially elite. It's that's the process through which they're crafted is extremely labor intensive. Casting cymbals individually is enormously time consuming. The monetary burdens of doing so are thus passed on to the customer. Zildjian could be charging a whole lot more for Ss too, but it doesn't have to, as it can profit from the line at its current price point. Again, I'm not a Zildjian official, and my views are merely speculative, but I do believe the interpretation makes sense when placed beneath the lenses of logic.
Of course, some non-B20 cymbals can be of very low quality, but B20 cymbals can be too. The alloy doesn't make or break the cymbal. Lots of other factors contribute to the overall result.
My cymbal philosophy is grounded in the repudiation of the supposition that one alloy is better than another. Rather, each alloy delivers a different character. It's all a matter of taste. If you love Zildjian Ks, you probably won't be enamored of Ss or the other way around. So be it. Play what you like and let the world keep spinning. Our spectrum of sound would be rather bland if we all championed the same family of cymbals.