Nintendo owns the patent of the design. There's a good possibility that the makers of Dingoo 'are' paying royalties to use it, they usually don't broadcast such things (public image and all that). Unless you have proof that they are not.
Here's the major problems with the product. Sure, the price is fine for the consumer, but if they do sell it at production cost they make zero profit from it. 10% of the profit from game/app sales could do well, if they had a really large market penetration, I don't think they do.
The other problem is, the only viable things to sell on the platform is homebrew games and apps (no one will ever buy or sell an emulator for example), but the market for it is nowhere near as profitable as iOS or Android.
I realize I come off sounding negative about it, but I'm looking at it from a developer viewpoint rather than a consumer one.