What to think of cheap torque wrenches?

I’m looking at the moment because of a torque wrench and I came across quite cheap/cheap offers like for example:http://cgi.ebay.de/…3186QQQihZ001QQcategoryZ84236QQrdZ1QcmdZViewItem Can you buy something like this?I’m quite skeptical because I don’t want the thing to turn around quite quickly (is that possible?) and I’m getting a screw off or something. What I don’t understand is that you have to pay over 150€ at proxxon around the same range. and here there are no 20 greetings Tobi