It's about manufacturing – A post from TechCrunch by John Biggs does a good job explaining the endless flops of altenate tablets coming out:
And he finish:In terms of manufacturing, the age of tablets is different from the age of netbooks mostly because there is no way to make a cheap tablet. You only have a certain, finite amount of space inside a small tablet case and, more important, tablet PC parts are expensive and often custom-built. Touchscreens are expensive because mother-glass manufacturers see Apple buying up their stock and they hope to make a killing. Flash memory is expensive because, well, Apple bought it all. And the tablets themselves are expensive because Apple set the prices.
Although I’m reticent to call this a “post PC” world, I think this is a bit more than a fad, though, and it seems that Apple is so far ahead in terms of sales, popularity, and usability that everyone else is, in a word, flummoxed. They just can’t fit a tablet into a global supply chain that rewards chintz.