A blow job given in return for a gift of fine jewelry. Derives from the Kay Jewelers slogan "Every Kiss Begins with Kay," suggesting that one can earn a kiss by giving someone an item from Kay. If the item is just OK, one only gets a kiss, but something really spectacular deserves more.
Bob: Did you see the ring that Ted gave his girlfriend?
Don: I know, it was huge! He's definitely getting a klow job for that one.