The McRib is actually an awful example for this, because McD’s primary deciding factor is the price of pork. When pork prices drop, McD revives the McRib. They want to manufacture them as cheaply as possible. Then when the prices start to climb again, they pull it from the menu. That’s why they don’t do big “it’s coming back on this date, and leaving on this date” announcements ahead of time, because those announcements would affect the pork prices as pig farmers would anticipate the upcoming large McD orders, and subsequent dips when they stop selling.