Let's present you a hypothetical. There's a comic you want to buy. Not a pre-existing one, a newer one. Just had its first issue released, in fact. So of course you want to support this book, and you figure, hey, I'll go to the comics store, buy the comic, take the comic home, and they'll see my purchase, right? Just like anything else. Like buying a video game, a movie, a book, you show up, you take it off the rack, you buy it then and there, and then you've shown your support with your wallet. Put your money where your mouth is.
That makes sense, right?
Unfortunately, though it does make sense to us hearing it, the fact is, buying your comic that way is practically irrelevant to the actual sales of a comic book.
Yes, I know that's fucking bizarre.
Print comics work on a pre-order system - a system that almost never comes up, and when it does, is equal parts confusing, infuriating, and awfully awfully expensive.
Here's how things work: When you go in and buy a comic off the racks at your comic store, all you're doing is depleting the stock of comics they already ordered in advance - what your purchase means is that individual sale avoids going into the back issue bins. Little to nothing else. Short of a surprise massive turnout to buy an individual comic and thus force it into reprintings, individual purchases of individual comics off the rack mean absolutely nothing to the comics publishing company, and on the individual level, to the survival of that comic you like so much.
The actual purchases, the sales that actually matter the most to the publishing companies, are made in advance. Deep in advance. About three months advance, to be exact. Before even issue one hits the stands, the real point of purchase is your local comics retailer - if you have one - putting in an order to the comics publisher for whatever books they have. Because the comics are non-returnable, the retailer can't buy just equal amounts of everything. They have to carefully weigh which comics they think will actually sell in their shop, so they're not weighed down with a massive backstock of issues to toss into the bins and hope someone picks it up, maybe years later, and takes it off their hands. This is why an awful lot of comics creators actually dread being told that a comics shop has sold out of their book - it means most likely that they made a very low order to begin with, and that doesn't spell anything good for the survival chances of their comic.
Here's how you're "supposed" to buy comics for your purchase to matter to the publisher: You go into your comic shop, and you tell them you want to buy (x) comic - long before it comes out. The moment you hear it's happening. It doesn't matter if there's not so much as a preview or even a creative team announced yet, you're supposed to pop over to the comic shop and tell the retailer "I want, and will definitely buy, this comic". That way, your interest is noted to the retailer, who sees demand for the comic, who thus may boost their pre-orders to the publisher for said comic. The retailer has to weigh local interest, available shelf-space, likeliness of actually selling, so many things together, before they make that pre-order. And what takes the guessing game out of this for retailers is if enough people show up to say "I want (x) comic", specifically in advance. Or, to make the matter feel more complex, you can take an "order code", found in Previews magazine (or on their online website), hand it over to the retailer, and they can add that to their pre-order stock. So you make sure you get your comic, and your purchase is noted to the retailer, and the publisher, that yes, people do want the comic.
By the time you're buying issue one off the rack, pre-orders for issue three are already being made. And if demand wasn't shown early for issue one, then it's very unlikely that the sales for issue two and issue three are going to be any better - there's very often a steep drop off between issue 1 and issue 2 alone, with a continual slow frittering away of sales until it hits bottom. This month to month loss of sales is a big reason Marvel's adopted the constant relaunch and renumbering model - all those purchases lost month to month come back to issue one, then flit away again, bit by bit, until they relaunch and renumber all over again. It's why you don't see comics that reach numbers in the hundreds anymore - or even often as much as 50 issues or so.
"So, wait," you might say to yourself. "I'm supposed to buy a comic 3 months in advance, usually for three to four dollars a pop, based sometimes on as little as a cover and a title, by researching it myself and looking through all these ordering systems, then telling it to the person who sells comics in my area - if one exists at all - in order to support my favorite comics in the way that the publishers actually give a shit about?"
Yes.
"That's a terrible fucking system that makes no sense."
Also yes.
Let's talk a little recent comics history. Currently, Captain Marvel is not a great selling comic. She's frequently outsold by the character who is, in canon, inspired by her in the first place - Ms. Marvel/Kamala Khan. But Marvel's interested in pushing her, in giving her frequent relaunches and renumberings, largely in part to the fact that she has a movie coming up.
The first writer on hand for this iteration of Captain Marvel was Kelly Sue DeConnick. Kelly Sue DeConnick is no fool about the comics industry. She knew that, at the time, Captain Marvel stood little to no chance of succeeding, and would most likely get cancelled in about 12 issues, maybe a little more, maybe a little less. Such is the fate of many comics, be they ones with new representation like Kamala Khan, or even relaunches of very old material like Challengers of the Unknown. If you're not a character that the core market, the people who buy every week and have been buying for years, decades, already buy, the odds of you surviving are incredibly slim.
So, in order to help her own book out, KSD got talking. She talked about pre-orders. And she started, essentially, a pre-order campaign for her book, to help bolster its sales, and avoid a very likely early cancellation, since Carol was very much not an a-list character, nor was Marvel as interested in pushing her regardless of sales until the movie announcement dropped.
Here, her post on the direct market, pre-ordering, how to do it, all that, is still up. You can read it here.
Here's the thing: DeConnick did this of her own volition. DeConnick promoted and campaigned for her comic. DeConnick took the time to thoroughly explain the direct market, the pre-ordering system, how it works, why, and how to order your comics through it so your purchase is actually counted, to her fans, and to try and reach out to potential new fans, or just to people who, in general, didn't know this was how the print comics market works.
Which is, I'd wager, the majority of people with an interest in comics. From the casual, to even some hardcore fans with a deep knowledge of comics continuity, the system is not well known at all.
Now, it's very good that she did all this campaigning and this hardwork for her book, really put in the time and effort to boost Captain Marvel on her own.
But that's also just it: She did it on her own.
She was working for Marvel, one of the largest comics publishing businesses, one of the longest lasting, with the most resources in their hands to advertise and campaign for comics, to explain the pre-order system to readers, to do everything with regards to promoting and selling comics...
And it wasn't them who campaigned for the book, hyped the book, explained the pre-order system, and how to order through. It wasn't Marvel, the very company publishing her, with supposed the greatest interest in seeing their comics succeed, who explained all that, who put in that marketing and campaigning work.
DeConnick did it.