Not surprisingly, the 4K model range starts where the regular HD models leave off: it begins with a $600 50-inch model, and you can spring for 55-inch ($700) and 65-inch ($1,099) models if you want more visual real estate. They should be available today through Walmart's online and retail stores as of today. These aren't the most affordable Roku sets we've seen at this very moment (TCL can give you a 50-inch 4K set for less), but keep an eye out -- we wouldn't be surprised if Walmart offers bargains, especially as holiday shopping reaches its crescendo.