I don't know exactly what "cheap" will be, but whatever it is, I think we'll see it from the 561nm wavelength before either 589 or 593.
I know that sounds ridiculous since 561s are so rare right now while tons of forum members have 589/593. But while ridiculous sounding, it's logical.
561 DPSS is a familiar process. It's ND:YAG, and it's frequency doubling. 561 is very similar to the process for 532. Both 589 and 593 are much more complicated.
There are a ton of people making 532nm DPSS units out there (in China and elsewhere). Many of these manufactures would be capable of producing 561nm without too much pain. 589/593 would be a different story.
So is there incentive to making 561nm DPSS units? Not a ton, there isn't huge demand. But if a 532nm DPSS module maker realizes that they can sell a 1mW 561nm module for $100 bucks, it might not take a huge demand in order to make that a worthwhile brief diversion from making 100mW 532nm modules that sell for $25.