There are lots of knock-offs or generic stuff marked under a well-known brand name on ebay and amazon. I haven't personally experienced this with electronics tools, but I do know folks that have received fake Snap-On automotive tools from Amazon or ebay.
Those links could very well be for the authentic product, or maybe not. You don't know. This is why I would buy direct from ifixit's website.
[doublepost=1478887631][/doublepost]I should add that I think there it also depends on your use. If you plan on using this tool just once or twice, get the cheapest cheapo one and throw it out when you're done. If you plan on using it many times, saving a few bucks isn't worth it and buy it direct from the manufacturer. Personally, I have never regretted buying a quality tool.