In the short term no, but in the long term if too many cross over to buying them from chinese websites, then companies like Nike will stop paying such large sums in these contracts... though we're a good few years off of having to worry about the next contract.Which is my point.
Not buying an 'official' shirt isn't hurting Levy's transfer kitty.
I say that as someone who is more than happy to use said websites, as I refuse to pay £115 for a football shirt that costs pennies to make, and even more so refuse to pay £75 for a version of that shirt that the club is willing to hold their hands up and say "yeah, this one's a bit shit compared to the real one...".