That's true. This is what I wrote previously:
Yes, when you pinch pennies in mass production then you can save a lot of money. But aftermarket sapphire crystals are produced in small lots, hence the 10-15% price difference. I have no doubt that Seiko could figure out how to source sapphire at volume for the same cost as hardlex if they were so inclined.
But suppose they couldn't. What would that mean? Suppose product development, manufacturing and distribution costs Seiko 80% of a watch's sale price. That's a pretty conservative estimate. For a $400 watch, that means Seiko keeps $40. But if they use sapphire, they now they have a net $4 additional expense, so they only keep $36. Used to be they made $4000 by selling 100 watches. Now they need to sell 111 watches to make the same.. That's an 11% increase in sales in order to break even. If sapphire is really such a terrific selling point as several folks in this thread have argued, then 11% should be no problem at all. And if 80% and $4 are too conservative (my guess is they are) then Seiko isn't gaining anything by withholding that precious sapphire.