it will vary depending on what needs to be done/ what you do.... There aren't many actual known numbers for the cost, but you have to figure at the very least you are looking at fees to release on the vita, plus fees for the games, plus paying people to translate it, which even for a cheap translation digital only release is most likely well north of 100k meaning that usually a game will need to move at least 5k units to even have a tiny shot of breaking even.
for a game like tales of innocence only namco will bring it over they won't let anyone else touch it, and last i checked they will pay to fully dub it and will take that into account when deciding to do a project, which means a game like tales of innocence will likely never release in english as it just wouldn't project to make them any money.
Ys has a good shot at coming over as does the legend of heroes games and meruru though.