Paying once to get a game on multiple platforms is a nice gesture. As a platform holder, Sony has been terrific about letting developers support with its Cross-Buy, but Nintendo? Not so much. Progress has been made, maybe, with a recent eShop title called Squids Odyssey.
In Europe, folks who purchase this role-playing game on 3DS can then download it at no additional cost on Wii U provided they have their Nintendo Network ID set up for both systems. Yes, it's strangely got to be in that order and yes, this isn't available in North America.
Speaking to Go Nintendo, developer The Game Bakers said "It's proof that Nintendo is making efforts in giving more control to the developer on its pricing and promotions ... It's a shame that it's only in Europe yet but hopefully this cross buy operation will be appreciated and the technical constraints that prevented it to happen in the US will be fixed."
Discounts for double dipping on a game are appreciated and we've seen a fair amount of that before with Nintendo, but there's really no topping a full-on pay-once scheme like this, and I'm sure the company recognizes that even if it hasn't been quick to act on it. If literally nothing else, cross buy needs to be implemented for the Wii U / 3DS Virtual Console. C'mon!