rickn23, i am an admitted comic book fan and purchase a variety of books from all of the big publishers including the independents such as image, idw, dark horse, dynamite and so forth.
DC actually has a more diverse advertising base which one would expect as Marvel/Disney is big at self promotion. Just look at the Sportcenter spots for the Captain America movie.
A Mavel/DC comic is 31/35 pages including inside cover and back page. DC has 12 ads Marvel 8 per book. 5 of the DC ads include outside companies (Triforce, Wondercon, Combos, Telltale Games, Viggle) Marvel 3 (mycomicshop.com, awesomecon, penguin books).
As i said this does not take into consideration Red Giant being a promoter of the industry especially for the independents. I am sure they can have a combo of advertisers from both inside and outside the industry.
I am not going to estimate the revenues they will generate I am just pointing out there is a market for people advertising in the medium and free comics will see plenty of eyes.
Most comic shops give away all promo/free issues to every person that makes a purchase in a comic store and I myself always enjoy picking up a free issue of something i might not normally read. I cannot attest to what Benny has done in the past but the concept is one i will keep a close eye on as it could turn out to be quite the story a year from now. I plan on visiting my local comic shop in the coming days and will inquire to the owners about Red Giant and will post their comments.