I did that for about 9 months. The Ken Block one has turned out to be, for whatever reason, as rare as rocking horse poo. I don't know if there was an accidentally short run, or if it was just insanely popular, but I wound up paying retail on it from slot32.de. But even they are showing it as sold out now. Perhaps Avant Slot should take notice and do a second run of this particular livery. In this case, it won't kill the second hand market for them because everybody seems to be hanging on to the ones they have.
But yes, it costs nothing to put a search on Ebay and have them email you if one turns up. Just don't rely on it as the sole avenue for procuring one.