Well, looks like ol' Stan's brilliant scheme to get you to buy Marvel Comics wholesale to try to sell to your friends didn't work too well, since, let's face it, all else being equal, everyone would rather buy comics from the newsstand or comic book store (the latter was only starting to gain prominence at this time) than from Billy by the sandbox.
Instead, we get the far more sensible direct subscription service. Today's ad, starring Spidey himself, is among the first of what would soon come to be a mainstay ad in all Marvel comics.
Now, to me part of the joy of comics was rushing down to the comic book store and spending hours perusing the other new releases before paying for my regular fix; nobody in their right mind would consider in-store purchasing of comic books to be a chore. So to me the idea of subscription never held much water... besides, as a kid* I never had enough money to pay for all twelve issues up front.
Even worse, Amazing Spider-Man at this time was retailing for 25 cents an issue, or $3.00 a year, a full 50 cents cheaper per year than if you just bought them at the store! I guess that covers shipping, and if you happened to not live near an area that allowed you to conveniently and consistently get your comics this might be your best bet, but barring that I can't see any reason to subscribe at these rates. Hell, when they say "please allow 8-10 weeks for delivery" that would freak me out that my comics might be up to two months late!
* Two anecdotes from my childhood regarding Marvel comics, subscriptions, and Spider-Man:
When I first came upon these subscription pages as a kid I didn't understand the concept of subscribing just yet, and I actually thought the page was a checklist of different comics you owned! This line of thinking came from the fact that I actually got into Marvel comics via the 2nd edition of Marvel trading cards released in 1991 , which did have such checklists, and were a measure of coolness on the playground. I'd say that marking the pages of my comics was as heinous as vandalism but my first comics got so over-read that they're mostly in tatters anyway, if I still have them at all (and I do indeed still have a handful in my possession).
Meanwhile, in the summer of 1995, I came in "direct" contact with subscriptions when I discovered that someone in our apartment building was subscribing to Spectacular Spider-Man, and potentially other Spider-Man titles that I can't remember. At the time all large pieces of mail for the building was just piled on a table next to the mailboxes for all to see and take. So when I saw brand new sealed comics amongst the pile, no amount of morals and ethics could stop me from absconding with them before the rightful owner picked them up. I feel really embarrassed and ashamed to admit it, but I think this went on for at least 3 issues, and they all, coincidentally enough, were right in the middle of The Clone Saga *(in fact the first issue I took may well have been Spectacular #226, the famous reveal of Peter Parker being the clone of Ben Reilly).
I also seem to recall that my parents found out and told me to reveal my doings to the subscriber, who took it surprisingly well, basically letting me go. Sad to say, but if I was in that guy's position I may well have wrung my younger self's neck.
*This ad for Marvel Comics subscriptions ran in Amazing Spider-Man #149, October 1975, which is even more ironic given my anecdote since this issue was the climax of the original Clone Saga story, the one whose storyline would be picked up twenty years later!