The commodity components used to assemble a tablet are vastly less expensive than they would be if not used by so many other manufacturers.

Where's the Raspberry Pi of tablets?

There are a ton of craptablets based on Rockchip SoCs. Even so, a craptablet running "real Linux" would probably cost more than the equivalent Android version.

The demoscene people do some really amazing work with some very basic hardware, so why can't that kind of talent be applied to making a really ripping Linux tablet?

Make Apple open up the iPad then. makes sense rather than windows tablets which are barely out.

We don't have to "make" Apple do anything. There are already people porting Linux and Android on their hardware. See http://www.idroidproject.org/wiki/Main_Page