I have noticed a couple differences between this one and the champagne one I got on ebay though. The logo on the white one is like velvet material, in the usual silver color, while the champagne one is smooth and in gold / champagne color that matches the rest of the shirt. Also, the band of the inner shelf bra is different. The white one has 4 lines of stitching on the band and the champagne one doesn't have any. Hmmm... I compared the rest of the shirts and qualities and they seem equal. The material feels very similar. The other details and stitchings everywhere else are identical. Even the fit is the same, minus the size factor. So I don't think the champagne one is fake (I'm always wary buying stuff off of ebay). Maybe it's an earlier version of the Dance:Strap tank. I know Lululemon has certain products that they have carried and changed/updated throughout the years. Such as the Groove pants. There are many different versions of it. So maybe the same applies to this tank.
Anyways, I love both of these shirts regardless. I just think the champagne color is so pretty and unique. I wore it to the gym and it absorbed sweat well too. White one is always versatile and fresh for the spring!