I believe your correct because a usb has data and power cables. It has one power and one ground cable and then data cables, so you could use a powered hub and I believe it would power all the devices instead of your computer or you could tap into the 5v wire to the cable. i don't know if you would have to tap into the ground wire and reground it.
"If you have lots of unpowered devices like mice and cameras, you probably need a powered hub. The hub has its own transformer, and it supplies power to the devices that connect to the hub so the devices do not overload the computer's power supply."