A Bare Bones Internet Connected Microcontroller < $10?
Once you include your MCU, possibly an Ethernet MAC/PHY (PIC18F97J parts have integrated MAC/PHY, as do a few other MCU's), Ethernet magnetics &amp; jack, power supplies, I/O &amp; power connectors, board manufacture... everything adds up in a hurry when you're paying one-off prices.  You'd struggle to make one for sub-$20, let alone sub-$10.  Once you can make them by the thousand the price-per-unit comes down, but until then you're pretty much screwed.