Those aren't UMPCs, they are just all in one wall mountable PCs designed for industrial use. The market for these types of devices is currently pretty limited, hence the high price, and these are for industrial use and that generally makes them even more expensive.
The UMPCs are in the $1K range, which is not totally unreasonable for that kidn of thing early in its price cycle. They'll come down.
What I'd do is put the tiny PCs in the closet and use a cat5 KVM extender to go out to the display, so that everything is in one place. It'll cost more than $600, as will any solution that has more than a Lilliput sized screen (the 7" 800x480 types), but it could be done for less than $2500 certainly. About $700 for the tiny PC, $250'ish for the KVM extender, and $550'ish for a 15" touch screen. It would be more maintainable due to having all the computers centralized and less expensive.
Not that I'm against having local wall mounted computers either, as long as they can boot from a central server and are completely minimalist, for low cost and low maintenance, used purely as an automation interface.
This was just a real quick search. If you do not like the monitor or the PC spend a little bit more to get what you really want. The bottom line is there is no need to spend $3000 to get a decent TS setup)
the only problem I see with such a setup is that you have to have 2 plugs for power. Unless you can wire directly into a socket or something, but not sure if that is feasible. And where do u stuff the pc?
I am looking for something for the kitchen, but I am also looking for a decent wireless touchscreen for a good price. <$700