I appreciate your (honest) response! Sincerely. 
I truly think nobody should ever spend more money on more systems than they need/will actually get some utility out of! But just to keep the discussion going, a thought experiment →
What sounds more likely, that:
A. ) A cabal of Dungeontubers, consisting of Questing Beast, DungeonMasterpiece, TheAlexandrian, Dungeoncraft, Dave Thaumivore, Roll for combat, Me Myself and Die, Trevor D.,… many of which have serious OSR credentials, all conspired in some sort of Cabal to manufacture all their positive reviews, videos and responses to Shadowdark, because some of them happen to be aware of or are friends with Kelsey?
All that, even though the majority of those have their own competing OSR rulesets or books and Kickstarters?
Every one of those Dungeontubers is sitting at that table and cheering the hell out of Kelsey and Shadowdark during the Ennies award speech below… So not only did they manufacture hype when it first came out ages ago, but they continue in their (nefarious?) marketing / support efforts, going so far as to cheer wildly during an award ceremony. ;p
→
On top of that, the manufacturing of excitement was so! effective that they fooled all five democratically elected and impartial judges, as well as all the voting public/regular RPGamers! And that alone is how and why SD got the 4 awards. →
“The ENNIES comprise two rounds. In the first round, publishers submit their products for nomination. Entries are judged by five democratically elected judges. The nominated products are voted on by the public in the second round.”
“Judges are volunteers, who follow a strict set of ethical guidelines. Chief among them is the vow not to have any professional relationship with any RPG publisher in the lead up to the awards.”
OR,
B. ) Yes, Kelsey and her wife did a spectacular job promoting SD and the Kickstarter which is why well-known Dungeontubers (some of which Kelsey knew somewhat or a lot) decided to review it and ended up actually loving it a lot. As such the public became aware of it too, and the Kickstarter did very well, and now, more than a year later there is vibrant community of groups that play it, a ton of 3rd party content and more, as well as recognition by way of the awards.
And that all the above is (also) because it truly is a great game that does do a few things very different than any other RPG, OSR or not? Sometimes popularity is only hype,… but sometimes popularity -especially when it is on-going and for more than a year and a half after release and among OSR gamers that have 0 connection to the creator- is well deserved and -also- based on merit, quality and innovation.
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I own “Worlds Without Number”, lovely book! But (by comparison) it is so long, and so much small text and so many options and rules, hence my group and I have never played it, and was certainly an expensive book.
OSE, I had it for a year or two, never played it, there were some things about it that were too old school for me, just not enough of the few options and feel of more modern refinements (2e to 5e stuff) that I do enjoy. I sold that book.
5E, had all three books for many years, sold them.
BFRPG I used to play with my group, still have the books, it will always have a place in my heart, such a lovely community, creator and amazing price! Good game too, especially for what you pay. Hell, I literally ordered 10+ books and gifted them all to people. Just to spread the BSFRPG vibes into the world and to have more OSR things out there.
But honestly it BSFRPG doesn’t come even close to SD in terms of quality, art, playability, ease of use, clarity and terseness of the rules and innovation. Which is fine, after all BSFRPG isn’t trying to do the same thing, to me they are rather different & came about in totally different OSR eras.
I still have a bunch of other OSR books, but atm I can’t imagine playing any of them (other than perhaps Knave 2E, as a temporary experiment) instead of Shadowdark, at least not for my fantasy games and not long term. Because none of those other rulesets and books have all of the specific combination of things that make SD unique and work so well and so fast/easily for me and my two groups, one of those groups consists of quite a few people, for us all SD has meant:
-Great combo of modern and OSR rules
-Short read, very succinct yet complete, with plenty of monsters and things for DM included. It really does feel like you are getting DMG, PHB and MM in one, sure, shorter than the ones from 5E but certainly no less usable or enjoyable.
-Amazing layout and ease of use at the table
-Deadly yet fair, evocative Grimdark ish but also bit humorous vibe and art, great unique mechanics such as torch timer, talents etc
-Easily hackable, expandable and with a big thriving ecosystem. There are so many additional classes and rules out there, digital tools, character generators etc by Kelsey and maaaany others that I do not need to worry about having to put time in to write and add a bard, ninja, desert warrior or even an entire Dark Sun setting,… if myself or my players want it, it very likely already exists, sometimes for free, often for a very affordable price.
I do agree that €55 is not “cheap”,. but if you consider the amazing quality of the book itself,… as well as the contents, i think it is absolutely a fair price! Especially if you see what the new D&D 5.5e books cost,. and with SD being one of the best alternatives to 5 and 5.5e…
Even if I didn’t love the system way more, even if hypothetically I found 5E and Shadowdark on par, I would muuuuch rather give my cash to Kelsey -who by all accounts is lovely person that loves OSRpg- than to evil Hasbro. Not saying that you love 5(.5), I have no idea, but only saying that indeed that Shadowdark is an awesome gateway or alternative to Hasbro stuff, and for some of us it is the end stop, like the only replacement (for both Hasbro stuff and possibly OSR products) we need for the foreseeable future.
I do very much agree that a paperback version, say for 20 to 32 € would be awesome! For fence-sitters, people from lower income countries, kids who can’t afford that much, etc. I think it would bring even more players into the SD and OSR fold, but otoh, I have no idea how viable that is and if it wouldn’t even be bad business for the creator.
They went for high production values, the binding, paper/page quality and layout outshine 5.5E, and perhaps that is intentional and they want to keep it that way? Not sure. Of course people can always buy the PDF and have their own POD copy made for little.
I know,… I sound like a Shadowdark car salesman. xd I give you my word, I have 0 affiliation with Kelsey nor any of the aforementioned Dungeontubers, I just truly think it is a unique product, proposition and game experience that actually very much delivers on the hype and marketing. It proves itself very much in the eating of the pudding. Not saying you should go out and buy it and play it, but perhaps you could read the PDF sometime, if you haven’t already.
Either way, even if you never play it, that is of course more than fine, if you are playing your system of choice and everyone in your group is totally happy with that one = you are doing it right and winning! 
But if someone wanted to switch from 5E or get into OSR or had 0 experience in TTRPGs and wanted to start playing, I would not hesitate to steer them to SD if they could afford the €55. Beats the hell out of the $180 Hasbro is asking for the new PHB+DMG+MM.
If they could not afford €55, the beauty of the OSR is that there is about 2 to 4+ viable alternatives -that don’t offer the same exactly, but that are also very good and that cost less-. Swords & Wizardry, BFRPG, White Box Fantastical Medieval Adventure Game, Black Sword Hack – Ultimate Chaos Edition and a few more.
I truly think nobody should ever spend more money on more systems than they need/will actually get some utility out of! But just to keep the discussion going, a thought experiment → 
