OK, I can see that arguement.
But let me counter you with my Yhettees, my second Scraplauncher and Ironblaster, and my Tyrant. None of them are GW models, most are cheaper than the GW alternative and are, to me, better too. Is this proxying? They are the same reasons that people will go with Mantic over GW.
I'm not trying to change your mind, or even provoke an arguement, but I think that asserting that everyone has to use the GW version of a figure when there are cheaper alternatives is a little over the top. Times are tough, money is tight and this is an expensive hobby. If people want to save a few quid on their models then I have no issue with it.