WDRC is a concept, not a type of technology. Manufacturers are free to use any concept they think will work and most use WDRC. The technology used to implement WDRC changes over time.
The prices at Costco are cheaper when you compare apples to apples. Costco includes a 36 month warranty and a 24 month loss and damage, along with everything you need. Sam’s offers a 1 year warranty at their quoted price and tubes are extra? Compare apples to apples and don’t assume anything is included at Sam’s.