As for the $40 version with keyboard and screen, you can beat that price on Amazon.[1] There are several tablets under $40 now, and by $50 or so, they're not that bad. That's what those low-cost SOIC chips are made for, after all.
The tablet/phone industry is desperately trying to prop computer prices up. The industry would like a price point around $500 for tablets. But it's not working.
[1] http://www.amazon.com/Android-Allwinner-Cameras-Capacitive-S...