Forget advertising: as much as Samsung spends on it, that is just a FRACTION of their larger marketing budget.
Their full marketing budget is larger than Apple's, Microsoft's, Dell's and Coca-Cola's
combined.
So, what's the extra marketing expense that Samsung spends even MORE on than they do on ads?
Paying incentives to salespeople. Apple doesn't bribe the guy in the carrier store to hand you an iPhone. For Samsung, that's business as usual.
And of course it works: if a guy is paid to tell the average consumer "this is like an iPhone but better," a huge number of people simply won't know any better.
Even in Apple Stores, iPhones are not sold on commission. But at least there you went already interested in Apple products and can try them out to confirm. At a carrier store, many people walk in with no interest in a Samsung, and yet walk out with one for no good reason. (And yes, of course, some people choose Samsung in an informed way not influenced by the salespeople--but enough people ARE that Samsung's massive payout is worth it.)
Look at the last chart here:
http://www.asymco.com/2012/11/29/the-cost-of-selling-galaxies/
(EDIT: slow to finish posting! Beaten a few times over.)