Yes but if you look at my setup (see post earlier on), you will see that my most expensive HDMI cable cost me £15 for 1m. The rest cost me a tenner other than the long run. I don't think £10 is too much to pay and the peace of mind, for me anyway, doesn't come from the fact I've paid more but the fact I did not buy it from ebay and that I have bought mine from respected professional cable manufacturers, equipment installers and suppliers with a reputation to maintain. Oh and I didn't pay through the nose. Don't get me wrong, I'm sure there are some good quality kit on ebay but from what I've found by buying cheap unbranded chargers and adaptors etc. is they don't last, simply as the build quality isn't up to much. I doubt you will have a problem with your ebay cables but as I said, not for me mate. That said, they're probably made in the same factory as the branded stuff!!!
PS. Ebay do not police their listings properly, just look at the amount of counterfeit (and possibly worse) goods that appear on a daily basis. Saying your cables have passed certification and proving it is another entirely different matter. If in doubt ask them for proof and then contact hdmi.org.