Costco specifically, and perhaps Sam's Club, will often have "hidden" deals on one item in the store. Sometimes it's really fancy wine, sometimes electronics. Basically, it wasn't "mis-priced" as the systems are all automated (prices are entered in a central database) and then lookups are based on UPC barcodes since forever.
Mistakes can happen, but usually in the "price on the shelf was more than at checkout" variety because of the human element involved in adding/removing price flags on the physical store shelves.