Occasionally, you will find Kerastase or other "exclusively salon" brand products in the grocery store or another retail outlet that isn't a salon.  The industry term for this is "diversion". It's usually not the entire line, there's usually not very much of it, and it's frequently a discontinued portion of the line.  There's a reason for this.  The product was obtained in violation of the manufacturer's and distributor's contracts.  Brands like Kerastase and Oribe protect their product vigilantly and enter into legal contracts with salons to sell it only to end user retail customers.  The biggest risks with "diverted" product is mold and product tampering.  Most of it is old, and on rare ocassions, has been "cut" with less expensive "fillers".

Admittedly, most of the higher price lines you find in the grocery stores is exactly the same stuff you find in salons, it's just older.  The biggest single difference is that somewhere along the supply chain, someone has sold the product to the grocery store in breach of contract.  Products that find their way into grocery and drug stores have been "diverted" from salons and re-sold to these outlets in violation of a legal agreement.  Who does this?  Salons that can't sell through their stock, salons that are going ot of business and are stuck with inventory, and also professional "re-packagers" who collect product from multiple salons facing these situations and sell it in bulk to major retailers that can't get it through the manufacturer. 

The reason most grocery store stock is older than salon product is because it's been through a circuitous supply chain route.  It sits in a salon for ages because the salon can't move it, then it gets bought by a re-packager and sits in their warehouse until they can assemble it in bulk and move it.  This goes for much of what is sold on the internet as well.

The good news for salons is that the price grocery stores are charging is as much if not more than salon prices.