I have the Sleep Number RV Radius King and love it. I got it three years ago and I full time. The only thing you have to remember is to recalibrate the pump every time you power it back up. This process takes about 60 seconds so it isn't a big deal.
I wouldn't have anything else in an RV. It is also a lot lighter and a whole lot easier to install that any standard mattress. I'm not sure a regular king could even be wrestled into my bedroom and don't forget the radius corners. You would have to get one custom made to get that feature.
Mine wasn't even close to $4,400.00.