Costco does not sell fake bags. They are real. (Sams Club had the problem last year with some fakes, but not Costco.)
I've ordered over a dozen bags from costco.com and (for my own peace of mind) had most of them authenticated and they were all very real. Prices were anywhere from $55 to over $1,000. I wouldn't hesitate for a moment to buy!
Their return policy is amazing. I ordered a Betsey Johnson bag that was on clearance on their website earlier this fall. The strap had beads on it and the beads started to come off. When I went to a Costco store a couple of weeks ago, I brought the bag with me and they returned it - a used bag - with no questions asked!
Did want to add that like any store -- someone could pull a switch on them. Buy a real bag and return a fake which could possibly go to the next customer... my guess would be that nobody is authenticating the returns. Buyer beware as always... my bags are all very authentic from Costco and I got some GREAT deals on a few of them!
If the price ends in .97 that means it has been marked down. A year ago, they had a lot of Burberry and one little cosmetic bag was there forever and ever -- it never got marked down though. Others will start getting marked down sometimes after just a few weeks...
I watch those Costco bags closely! They had a fabulous Fendi messenger on there for $249 a year ago -- only lasted about 3 hours!!!
Sam's here sells high-end bags and wallets in spurts. Even though they're not an authorized dealer, I'm not concerned with the bags' authenticity, as they probably use the same channels Bluefly, another non-authorized dealer, does. I say this because I've seen the same models of purse at Sam's and Bluefly at the same time and same price. If there were fakes there, I agree with a previous poster that a "customer" (con artist) probably pulled a switch on them.