Why ground beef price is so much cheaper than the beef part that is used in grinding?

Newbie question: At Costco and Sam's Club (as an example) ground beef made out of Chuck roast is ~40% less expensive than buying the whole chuck roast beef itself. Assuming you need to take the whole chuck roast part and use workers and machinery to grind and package it, wouldn't you expect the price of ground beef to be higher than to the un-grinded beef roast part? Thanks! submitted by /u/djmikmik