I don't know if it's likely, but it would be very bold for Apple to charge the same price the two sizes.
I see all sorts of people make their choice of phone size based on the price. Wouldn't it be cool if Apple's sales force could help people decide on what size watch to get based solely on how it looks on their arm and nothing else?
These are supposed to be fashion pieces, after all. Does Apple want to see ludicrously tiny watches on large men's arms because they wanted to save a few bucks? That doesn't help Apple sell more watches.
Yes, I know the bigger watch uses more materials, but it's nowhere close to the difference between an iPad Air and Mini. And it's not like the markup on these things isn't high enough to cover the few extra cents in glass per larger watch.
I dunno, it would certainly be a departure from every other Apple product. But in this one case I could see it being beneficial to Apple.