I believe I understand the premise behind the "cheap" cable and limiting current consideration, but I would never use cheap. Aside from that, I felt that this is the aformentioned is the quisential rule to follow when boosting that I just needed to support this approach wholeheartedly.You really don't want the other car's engine to pull 400 cold cranking amps out of your Prius battery. It's best to limit the draw to under 100 amps. One suggestion to do this is go buy a pair of really cheap jumper cables with thin wires. Then let the Prius charge the other cars battery through this cable for 10 or so minutes (be sure your Prius is "Ready" before connecting the cables). Then try to start the other car (preferably with cables detached, but you may need to leave them attached for a little extra help). If the car won't start fairly quickly, give up and either go back to charging the battery or find someone with a big conventional battery to help.
The danger in all of this is if the other car's battery isn't just discharged, but has a short. Then you could draw over 100 amps even through the cheap cables.