I just see this as Apple and Samsung duking it out over who makes the fanciest, most expensive phone, but I dunno... seems to be a dangerous game, mostly for Samsung. But I don't see much of a choice.
Samsung seems to devote most of its time trying to compete with Apple. Now, both are the market share leaders so that's an easy get. But Apple has the luxury of a platform monopoly... they are the only game in town so for most iPhone users, if they don't want the new more expensive iPhone, they have to go with the older slightly less expensive iPhone.
Samsung, on the other hand, has a number of OEMs trying to knock them from their perch. And while their Android dominance is still safe, it's not nearly as safe as it used to be. It wasn't too long ago that you had one option and one option only if you wanted to get a really good Android phone... you had to buy one of the top shelf models from a select group of OEMs... Samsung, LG, HTC, etc... Motorola, with the first gen Moto X, signaled a shift. Over the next few years, we began to see more and more mid and low end phones - two classes of phones that were utter vomit for a time - that not only were cheap, but they were damn good phones.
Every year, those lower segments are getting better and better and the performance and quality gap is closing quickly. There are several very affordable phones on the market that while not matching 'flagship' phone, it's close enough to not make a difference... especially when you can get one for everyone in your family for the same price as one of those top shelf phones.
Now, with that in mind, you might think that Samsung would be better served to get the prices for these phones more in line with the best of the rest... but I think that would be a mistake. They don't want to be seen as one of many. To the majority of smartphone consumers, Samsung and Android are interchangeable. They go into the store and pick out the newest one and often just walk by the other phones thinking "Oh, those are the cheap phones". So Samsung is forced to try to keep that perception lead... and that costs money. Like dpham mentions, the S8 costs significantly more expensive to build than the S7 Edge and the S8+ even more. I am fairly certain that the Note 8 is probably going to set a record for BOM price for a mass market phone.
So Samsung needs to chase the dragon's tail... they have to be seen as above and beyond and not just 'one of many'.
Premium product for a premium price. They want consumers to think "Gee, that phone is $1000.. it must be TON better than the $500 phone on the other bench"... And THAT is the dangerous game, because Samsung runs the risk of consumers discovering that the answer to that dilemma is now "No, its not really".