Finally, after we do this for all the cards in the set, we can simply add up the total and determine how much a box is actually worth. Then we multiply the odds of opening a card by the card's value, which tells us how much value we expect that card to add to the box. To calculate EV, we first determine the odds of opening a specific card. Next we calculate the value of each card. While many of you may be familiar with the concept of expected value, here's a brief refresher. Expected value tells us just how much value we can expect to open from the cards in a booster box. While it will not show up in my calculations, there is value in having fun, drafting with friends, and keeping traditions, so don't let a poor EV alone keep you from purchasing a box. All of these are fine reasons to purchase a booster box, even a low-EV booster box. I'm sure there are a hundred other reasons as well. For some people, buying a box is a tradition. Others buy boxes to play limited with their friends. Some people buy boxes because cracking packs is fun. One more thing before getting into the methodology and the set itself: EV calculations only take into account the cold, hard numbers, and there are many reasons why people buy a box. And there are a bunch of sets where cracking a box is almost guaranteed to lose you money. Because of this uncertainty, I like to calculate the expected value (EV) of a booster box every time a new set comes out to figure out for myself whether or not buying a box is worthwhile in strictly economic terms.
There have also been a few sets where you could expect to (more or less) break even (Gatecrash, Fate Reforged, Theros).
In just the past few years, discounting supplemental products like Commander decks, there have been two sets where if you opened them right after the set release, you could expect to open more value from the box than you paid for the box (Return to Ravnica and Khans of Tarkir). The short answer is while opening sealed product is often a losing proposition from a value perspective, it isn't always a bad idea. Today all of these ideas are laughable (a flat world), if not downright disturbing ( Tarmogoyf is bad). It wasn't that long ago that pretty much everyone thought the world was flat, Tarmogoyf was unplayable, and that getting a voluntary lobotomy was the cure for pretty much any mental health problem. One questions that comes up all the time on Twitter, Reddit, and various other forums is "should I buy a box, and if so, what box should I buy?" The common knowledge in the Magic community is that, outside of playing limited, you should never crack sealed product because you are going to lose value but common knowledge isn't always the best knowledge.