I find it a goddamned impressive turnaround that Vita hasn't sold under 20K since Vita Slim released! The week right before Vita slim released Vita sold like about 4K, after that it has sold as high as 90K and never dropped under 20K! Pretty good for a doomed handheld with no games as everyone says. :P

I think the sales target you're looking for is 100-300k lifetime, and then I agree. I say that because companies Tecmo Koei, Namco, Atlus, Falcom, and Marvelous expect and get a lot more than 50k.

And those costs aren't nil for multiple platforms, but publishers are able to slowly move a franchise into the new generation without being as risky (God Eater 2 being the best example). As I said before, the Vita version of all these games has sold very well surpassing the PSP version and being on par with PS3 version.

Not free, but a number of the PS3/Vita games by smaller publishers (i.e. Sen no Kiseki by Falcom; certain Atelier games by Gust; Disgaea games by Nippon Ichi; Hyperdimension Neptunia games by Compile Heart) run on Sony's own PhyreEngine, which is designed to work (as I'm sure you can read on that page) across PSP/PS3/PSV/PS4 relatively easily.  Since the power gulf between Vita & PS3 is pretty close (and these games are hardly pushing the hardware anyway), I'd guess that these porting jobs are extremely easy tasks and that's why we've seen so many games make it across.

And I can't remember how you guys got onto this topic but if it was in terms of smaller third party support, then I'm pretty certain that's a massive reason for Vita getting so much stuff lately.  Sales targets don't need to be high when you can stick 2-3 of your team on porting the titles and reap a nice 50k physical + x% digital sales.