Pretty sure they are talking about the K40 "blue box" laser. I have heard they require some mods to get working properly but for the price some think they are worth it.
Just search 40w laser engraver on ebay and you should get several hits around $400. Mine is working great after some mods.
Mods:
~$25 for 8ft ground rod and wire
~ $35 for 24V DC power supply( includes 5 volt supply because I blow out the DC section of the board it come with)
~ $45 Raspberry Pi CNC Board + drivers
~ $35 Raspberry PI
I can scp dxf files to the raspberry then rdp or ssh -X to open bCNC. Open the file and click Run. bCNC just added laser support so the setup is trivial.
I'm not too sure on the cutting power though. I have done paper, leather and cardboard but the 1/8in plywood I have tried is too thick.
I also had to put a 3904 transistor and a resistor in the board to make the laser on signal be sinking.
