I've learned that the composition and distribution of magic cards and their rarity is a rather complex one. I won't pretend to know all about it and I can't claim to be a statistician but I can show you what the results of my booster box was and reflect a little on that. I can kind of geek out over that and so I will here.
Now before you go "wut?" here, if that was going to be your initial response just click away now. You won't care about this post.
What I've done is open all the boosters of a booster box of Shadows over Innistrad and keep them separated from the rest. I've done the same for a box of Origins, Kaladesh, and almost for a box of Eldritch but that's got two more boosters and I haven't even scanned it yet.
I used "
Delver Lens" to quickly catalogue the set. It's, at the time of writing free, magic card scanning app for Android that seems to function pretty decently. Sure there are some key UX things I would suggest, but for a free app it's great.
I consolidate each box to its own list, export it, and put it up at
mtgcollectionbuilder.com. This is a free MtG collection site that seems to be pretty complete. Unfortunately the import seems to have some trouble and it's rather a pain in the ass to make sure all your cards are in there. So I'll probably look a little further for a more stable database service. Although since I won't actually collect the cards I may not. Who knows!
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This resource goes deeper into the meta, but...) Each booster box contains 36 "booster" packs. A booster is a sealed tinfoil wrapper that contains, currently, 15 magic cards and a "marketing card" of some kind. The rarity distribution is fixed as is the booster composition. The actual cards are of course random within their rarity. A booster now contains 1 marketing card, 1 basic land or checklist, 1 rare or myth, 3 uncommons, and 9 commons. In sets with double faced cards there will be one of those of any rarity (making it possible to get two rares or even myths in one booster). In other sets that's just a common. The value for boosters from double faced card sets (like Shadows over Innistrad) really did feel much better because of the possibility of a rare flipcard.
And in case you don't know; commons are generally worthless. Uncommons are slightly above that, slightly more powerful. Rares tend to be more powerful although one rare can still be dramatically better than another rare. In 1 of every 8 boosters the rare is replaced by a mythical rare, a recent addition to this list. These tend to be very powerful. New in Kaladesh are the "
Masterpiece Series", which appears to have a rarity factor of 1 in 144 boosters. Okay, sure. I don't remember getting one but I wasn't even aware of this at the time.
Ok, Shadows over Innistrad. Note that a box has 36*15=540 magic cards. My scanner app reports 520 cards. I count 28 "checklists" in the set and of course 36 marketing cards. That means I've got an about 8 card surpluss.
I'm not going to check, sorry. I'm going to assume these concern commons. I did do a second pass to make sure the app scanned all the cards properly (there are some minor issues it could do well with resolving). The collection builder site reports 462 cards collected, having collected 205/297. Well damn, it failed to import some 60 cards on a regular and recent set? That's quite a lot... Worse yet, it failed to import two of the four myths. That kind of skews the numbers, ok ok brb manually checking and updating this list.
Okay. After manually matching the cards with what was listed on the site and updating accordingly, the site is now reporting 510 total cards collected and 82% of all cards collected. I'm still 12 short if you ignore the 28 checklists and I have simply no idea where those 12 are. Oh well.
I'm not sure which source the site quotes for prices, it's on there somewhere. For the entire set it reports an estimated value of $69.18, which is about 15 bucks short of what you paid for a box. I got 6 myths (beating the odds though one is a flipcard so that's not part of the 1:8), and 35 rares of which 6 are dupes. That totals to 41 which makes sense because 4 are flipcards bringing us to 37 and one of the rares is actually a foil, which I think is also separated from the normal distribution. It'd be nice if the builder site would just tell you how many cards are in the current filter... There's always room for improvement.
Foils; a manual tally brings me to 7 foils, 2 of which are lands :(
Most valueable cards I got, in order, are: "Nahiri, the Harbringer" ($13.50), "Jace, Unraveler of Secrets" ($6), "Arlinn Kord" ($5), "Thing in the ice" ($5), "Sorin, Grim Nemesis" ($4.20), and "Declaration in Stone" ($3.25). It's $1 from there on down.
According to this list, Nahirir is only the second most expensive card. It is beaten by "Archangel Avacyn" at $16. I can live with that. I seem to have found all the top tier cards after that, yay.
It seems no card in this box had more than four dupes. That's nice.
Oh yeah the marketing cards. So these cards have a back that is an advertorial like "Play FNM" and a front that's usually a token of some kind. From the 36 I got 4x zombie, 2x devil, 1x vampire knight, 17x clue, 6x spirit, 1x Arlinn's emblem, 1x wolf, 2x human soldier, 1x angel, 1x insect. I think the tokens are a nice touch, although another box had like 5 marketing cards with marketing printed on both sides. That's a little meh.
Some of the land cards were replaced by checklists, where you could tick them as being a flipcard with normal back. I think it's a little unfortunate that 28 potential foils were replaced by one of two types of checklists. Make _those_ part of the marketing set if you feel so strongly about them.
Of course Shadows over Innistrad was already an older set when I opened it so the prices were probably already on their way down. When I opened the Eldritch Moon box I got the card (Liliana) worth $36. That's almost half the value of a box on one card!
Ohwell. We'll save the stats on other boxes for another time.
So was it worth it? Yeah, I'd say so. Plenty of cards to play around with. And if you really wanted to you could sell the top tier cards to get another box at half price, and still get a lot of rares and uncommons out of it. Plus another box.
Oh and the fun of opening all those boosters. That's great :)