Just remember one thing. Apple, just like any other company is out there to make tons of money. And if they have the opportunity, they won't miss it. How much more it cost Apple to manufacture one model from the other does not equal the price. It's more then meets the eye when it comes to deciding a price for a product.
You see, that's the attitude that gets a lot of posters here in logical twists. Yes, Apple is a company and companies make money. Got it...
But, just because something is a little more expensive to manufacture doesn't necessarily mean it's going to cost more at retail. It's not like Apple looks at the cost of manufacturing an iPhone and says: "This costs $157 to manufacture, and therefore we will price it at $749. This slightly different iPhone costs $162 to manufacture, so therefore it will cost $950." Sure, it may seem arbitrary, but in reality the two numbers are not linked. The retail price is determined by a far more complicated methodology, and that is "what will a customer pay for this? what differentiates it from another product? what will a customer pay for another differentiator? does a jump from 16gb to 32gb warrant a $100 increase in price to enough consumers so that we can maximize profit?" If you don't understand that simply notion, you certainly shouldn't be guessing what Apple will charge for their devices.
It's the same problem we see with the whole "will they sell straps individually?" and "will the straps be interchangeable?" people. In a realistic world, it doesn't make sense not to sell straps individually, nor does it make sense that they wouldn't be interchangeable. Of course, there are some who believe Apple is out to make money and thus anything they can do to squeeze money from people is exactly what they will do. So selling non-interchangeable watch straps means people might buy more expensive models or it will hamper third party strap makers etc... but these arguments assume people blindly buy whatever Apple sells and that corporate goodwill means nothing to Apple. People would stop buying Apple if they acted that greedily. Somewhat greedily? Ok. But people have a limit.
Anyway, I could go on and on about how dumb people's arguments in these forums have been. I honestly expected more, though I guess that's dumb on my party because the internet isn't exactly the forum of geniuses Orson Scott Card predicted in Ender's Game. Most people probably stopped reading about the time their eyes subconsciously told them how long this post was going to be.
My point, anyway, is that saying "of course it will cost more because Apple wants to make money" is a pretty weak argument. Duh, they want to make money. But nobody here has given a reasonable estimate for how much DLC treatment costs, nor any indication that the Black Stainless watch will produce demand such that the price increase is warranted.