I saw a fake bottle of Louis XIII at the DF in LHR (selling for circa GBP 1000 so rather good thing to counterfeit). The manager there was astonished and very apologetic (and checked his stock, several other bottles were fake too -- some of the authenticity marks for Louis XIII are quite hard to forge; sadly JW Blue doesn't have such protection, but then it is far less expensive). So fakes can be for sale in the best stores (the distributor is at fault, either knowingly or unknowingly). Sometimes store clerks substitute fakes for stock that they shoplift, for example (but you aren't worried about that). The price is plausible so it probably is genuine price, but whether you get genuine stock is a different question. DF stores are of course a great place to palm off fakes as the clientele are hurried, can't come back the next day, and often are getting items as a gift so not looking too closely.