Starting at $329 the iPad mini already costs more than most 7-inch tablets on the market, and adding a high resolution Retina display could make it even more pricier. According to iSuppli (via the DigiTimes), bumping the iPad mini's resolution from 1024x768 to 2,048x1536 would raise production costs by 30%. If true, these extra costs would either have to be eaten by Apple, or be passed onto consumers. Apple isn't known for increasing prices from on from one generation to the next, but it is hard to see how they can keep the iPad mini priced at $329 if all the rumored hardware upgrades are true.
A lot of people were displeased with the iPad mini's lack of Retina display, but a lot of people were also shocked by the $329 price tag. So will people be willing to pay more money for more resolution? I guess it depends on why someone wants a smaller tablet in the first place.