There are other Chartplotters than the brands you mentioned or did you convienenly forget to post them. None are 3 times the $1300 I pad . Most are 12 inches but who needs another TV set.
Garmin Echo map $2790
B&G Vulcan $2199
Lowrance Elite $1819
I included the Garmin Echo above (although I rounded to $2800 on its price).
I see your argument has now shifted from $500-600 to the $2000-3000 price points. OK, now the high end iPad I mentioned is only 1.5-2x cheaper instead of 3x. You got me.
But if you are going to bring in smaller plotters than 12", then you also need to drop the tablet size accordingly, and the point I make about size, resolution, and price still holds.
As for 12", you might think it is a TV set, but for those of us doing long distance and long term cruising, like Outbound has been describing, 12" becomes around the minimal size for split screens, overlays, and multiple data streams. Our previous plotter was 8", and that was difficult to use in these modes. Like Outbound, we often have radar and chart on split screens, as well as pulling up AIS lists or instrument displays on screen as needed. Often we have radar in split screen showing two ranges. Sometimes with a chart overlay.
This might not be the way you use a plotter, but it isn't a reason to denigrate those that do as using a "TV set" (BTW, our TV is 28" - I couldn't watch a 12" set, even my computer is 15"). 12" today is actually becoming the smaller end of plotters.
I'm hearing silence on examples of where I've been hell-bent on pushing tablets in lieu of fixed plotters. Perhaps your accusation needs to be withdrawn?