That is the best way to tell if something is fake or not legit, if it's below retail or even brand supplier price.
Reminds me of the time I tried to get Photoshop, I bought copies on bid or buy twice and had to return them twice. In the end the only way to tell was the price and the fact that I had a serial number registered on their website. Was an expensive tool but it's something I grew up with and It's the most useful graphic tool I know. I might not buy a new copy or upgrade for the rest of my life but it will do.