Comics, as the Overstreet Guide will tell you, owe their existence to commerce . As an insert in a cereal packet or a vehicle for advertising, comics were an ideal way of promoting good will and a pleasant association with a product or company.
The industry takes an interest in self-promotion but hasn't always had its way. Tie yourself to the shoestrings of the manufacturer and you could find yourself doing a soft shoe shuffle on storylines.
Not that I think that being able to afford twelve cent comics as a kid was any kind of drawback. My curiosity toward controversy and a/cute political awareness wasn't dampened by a steady diet of Sweeper Sam the Mild Matman. Not in the least.
I'd like to kid myself that we fledgling fanboys fueled the profits of funnybook publishers but those seamonkeys and x-ray specs must have helped.
In any case, pushy sponsors and nervous editors didn't prevent the scattergun scatology of Viz, like a saucy English seaside postcard on acid, or the weighty worldliness of Crisis. The market decided that a comic character with "unfeasibly large testicles" was a better read than the actions of secret service types in countries round the world. Neither has built their house out of Pez candy, that's for sure.
Hostess Fruit Pies used the mainstream characters themselves in ads and, really, that's the tenor of ads in comics: as nourishing as a Mighty Crusaders story. You won't find fresh leafy vegetables being promoted in the ad pages (although there was one for milk).
During Shooter's reign of terror a whole line of toys were also licensed for ongoing series and fanboys somehow managed to absorb this and develop a fondness for the likes of Micronauts and Rom, Spaceknight. Comic fans don't care if Steve Skeates can write ad copy or Lee Marrs can illustrate it. The probable consensus is that most artists could draw the can of beans or motor scooter but it would depend on the skillset of the writer: a strong narrative storyteller may suit some jobs while a penchant for snappy phrases may benefit others. A title like "the Power to Purge" is pregnant with possibility and is possibly even wasted in a crummy comic book story.
So much for comics as a medium for advertising. What has advertising done in turn for comics? Precious little on the face of it. A new movie based on a comic book character or theme is bound to have a promotional effect for the original. Makers of industrial fasteners, I'm sure, would envy the focus that comic companies get for their product. Yet despite the serial nature of matinee cinema, they didn't take the opportunity to promote Silver Streak Comics on the silver screen, and creator Lev Gleason was preeminent in the field at the time. It's as if Hollywood would rather make a bad Doctor Strange film than promote the superior source material.
All Star Comics pre-date television but that doesn't mean that the medium has ever promoted the stars. They don't even have commercials for Adventures of Superman when you're watching Lois and Clark or Smallville and that's the same character produced by the same parent company. Would Prize Mystery have benefited from being beamed into living rooms? Indubitably but it was not to be. The cross-promotion that went on in the stories themselves may have made up for it.
You can find old issues (or atom age rarities if you prefer)in the classifieds and the odd alarmist tabloid piece on violence in comic books and that's about it, unless the companies pull some stunt like killing Superman. It did seem for a while there that formerly inviolable superheroes were dropping like flies. Dying and coming back from the dead is one thing but breaking Batman's back and chopping off Aquaman's hand was quite another. Newspapers select which characters they'll run in daily strips, which series they'll run in the Saturday supplement. It's a safe bet that Johnny Hart could do more with two properties in syndication than Arnold Drake could producing a lifetime of valuable commodities for the majors. And the papers won't run ads for Youngblood any time soon.
It could be argued that the percentages aren't there to promote an individual issue the way you would a motion picture or an episode of Friends but that shouldn't stop advertisers from putting an ongoing series up in lights. But if there were ever billboards of Buster Crabbe, it wasn't for his comic series.
Which only leaves magazines, which will run advertisements for comic books if they are comics or SF based (you won't see an ad for Gay Comics in Life ) and comic books themselves, which have been known to run ads for competitors' books.