A bunch of us at Robots & Dinosaurs (a HackerSpace in Sydney) have been playing with the TP Link WR-703N wireless routers* reflashing them with OpenWRT - they're available from Deal Extreme or eBay for under $25 - it's got no video, but it includes ethernet and onboard wifi. One of the guys has a stackable "daugherboard" which breaks-out/adds a USB hub, FTDI/GPIO/JTAG and two serial ports: http://www.kean.com.au/oshw/WR703N/
It's not as high powered as a RaspberryPi though, only a 400MHz cpu and 32M ram (+4M flash) - they're useful little machines, but the onboard video on the Pi kinda puts them in a different class. On the other hand, a Pi with ethernet/wifi/powersupply costs several times what a TP-W703N costs...
Powered off of mini-USB (I have extra chargers laying about), SD cards are cheap cheap cheap (I also have a selection on-hand), and a case can be made out of LEGO bricks (again…).
You forgot to add-on "keyboard, mouse, and monitor". Again, these are things that people usually have.
For the dev cards mentioned up-thread, you'd have to have some sort of programming dongle, which more than doubles their cost, as well as get your hands on the right magic toolchain.
All true - still means that bare minimum, a Pi (delivered) is double the price of a W703N (delivered).
If you need add any/all of: wifi, power supply, SDcard, enclosure - to the Pi for your project, then I think "a few times the price" is a reasonable description. Not everybody will have "spares" of those "on hand", and if your project involves building more than one of whatever, then you can't rely on "on hand" extras.
On the other hand, if you don't need wifi and you do need video out, then the Pi is an obvious choice.
my project for the TL-W703N is a Tahoe-LAFS server/storage appliance - the router and a 1 or 2TB USB harddrive - if I could put 10 or 12 of them together and distribute them amongst friends, just a harddrive sized package they need to plug into the wall and allow on their wifi (or wired) network, in return everyone gets several hundred Gig of "private cloud storage" with baked-in encryption and distributed storage reliability.
It's not as high powered as a RaspberryPi though, only a 400MHz cpu and 32M ram (+4M flash) - they're useful little machines, but the onboard video on the Pi kinda puts them in a different class. On the other hand, a Pi with ethernet/wifi/powersupply costs several times what a TP-W703N costs...
* http://wiki.openwrt.org/toh/tp-link/tl-wr703n