You might be just as well off to fashion your seven dollar bills into a small torch and light it.
Seriously though, I've had mixed luck with knock-off Chinese stuff on eBay. Sometimes it works perfectly and is a great bargain. Other times, it doesn't work at all. The percentage of times it works is probably much higher than the percentage of retail price that you pay.
On the other hand, I have one Knog light, a Gekko. I bought it for 93 cents at an REI scratch-and-dent sale. It didn't work at all. I wrote to Knog and told them my story, including the part about REI offering no promise that the thing would work at all. Knog sent me a new light (from Hong Kong, BTW).
Officially, Knog products have a two year warranty, but their warranty page also says this:
We expect all our products to ride to the shop and back again and again and again and again and again and again for a hell of a long time. But sometimes the **** hits the fan - and - if it does we want to make it as easy as possible for you to get righted even if the damage has been your fault or if the product is out of warranty. So get in touch with us...
(my emphasis added)
The question then becomes, is this kind of service worth an extra $15 or so? To me, it is.