I wouldn't want it to not have editing capability, so I would prefer something more like a laptop word processor with a built-in printer.

I very light weight, low power device with a built in printer which supports some type of simple word processor could be done. However, there are some very light and some very low cost laptops hitting the market now. For about $250 you can buy an eeepc laptop with a 7" screen which runs windows. Add a small portable printer to that like the Pentax PocketJet for another $250 and you have a very mobile solution which will easily fit in your backpack for $500. Questions for the original poster:

1. How much would expect to pay for your typewriter?2. Would you be willing to pay an additional $40 for an ink cartridge every say 500 pages?3. Is it ok to have to feed every sheet in manually when printing?

I think people who need it would not be satisfied by the loss of the pc editing options. The need for hard copy is receding, people are more happy texting on sadistic handhelds -- I see people on planes working on spreadsheets for hours on iPhones/blackberrys. There are larger portables with better keyboards emerging, and anyone who needs to be handed a paper will be happy with an email and an attachment. I have heard of older authors who prefer the delay/permanace of typing, being forced to think & not being tempted to edit endlessly... but these few probably have what they need.