Just a quick thought.
Microsoft’s Australian prices for the Surface tablet computer start at A$560, You pay another A$150 for a cover that doubles as a keyboard and a further A$45 each for VGA and HDMI adapters.
To be fair to Microsoft, you can use a tablet without any of those accessories. And let’s face it, Apple does the same. So do the companies selling Android tablets.
If computer makers sold laptops the same way there would be an outcry.
I think that you are forgetting that tablets are consumer devices and that most consumers will not want a keyboard or an hdmi adaptor. Consumers are intensely price-sensitive compared to professionals and an extra $200 for stuff they don’t want would almost certainly kill the deal for a great many.