Buzzard, I'm on your side, you know that. There is no bigger Seiko addict than yours truly on this forum, as far as I know....(not bragging, more musing). I was just making the point that these companies overlook the need to change out their normal parts when the price points start to get close to or over 4 digits. I am not even sure they are being cheap. Could be just oversight, or lack thereof. Hard to believe but it certainly happens in more than just the watch industry.
Case in point would be the Seiko TransOcean. Lower price point than the MarineMaster (Auto), yet the TransOcean has a sapphire crystal and and the MarineMaster doesn't. Both are dive spec rated. Maybe it's just an experiment to see if more people will buy TransOceans because of the Sapphire--like Invicta occasionally using Superluminova....?
Oh, there's no doubt you've taken Seikoholism to a level beyond my own. But I'm old and have perhaps collected some historic rationales. Specifically the depth ratings differ between the sapphire TransOcean and Marine Master. Due to their practice of building to double the rated depth the 600 meter spec on the base line Marine Master requires a thickness bump in the sapphire that didn't appeal to them on a cost / performance basis.
Additionally, the Marine Master crystal is dual curved AR treated chemically hardened borosilicate glass - not the easiest thing to duplicate in sapphire. My specific Marine Master SBDB009 has a sapphire crystal but it doesn't display the dual curve properties of the SBDX017. The sapphire crystal in the MarineMaster is more akin to the sapphire in the TransOcean - not that there's anything wrong with that, no sir. But I'm guessing if you eyeball the dual curve borosilicate crystal in the Marine Master on your next safari into the depths of the NY boutique you'll notice a difference.
If you want dual curved sapphire you'll be in Grand Seiko's neighborhood. You'll also note that one of the primary differences, using the 9F range as an example, is the crystal shape rather than composition. The standard sapphire product is listed at 2,200.00 and the dual curved sapphire at 3,100.00 (I believe the difference between the 9F62 and 9F82 is just the size - the crystal takes a fair amount of the blame for the pricing difference).
http://www.exquisitetimepieces.com/grand-seiko-quartz-sbgv205.html
vs.
http://www.exquisitetimepieces.com/grand-seiko-quartz-sbgx259.html
I could certainly be wrong but I believe it's a mistake to simply compare what a given crystal is made from without including adjustments for both thickness and profile. A literal reading of some information on crystals would have you believe a 2mm flat 40mm sapphire is superior to a 4mm dual curved chemically treated borosilicate and IMHO it just ain't so.
As a general rule, and one that I go along with, sapphire beats the wackers out of mineral crystal if they're at all alike otherwise. If they're considerably different then one should factor in these differences.
Naturally none of this means you can't have a dive watch a dual curved crystal AND sapphire - Grand Seiko will fix you right up for around 7 large. Hence, while I find your conjecture to be plausible, I don't really believe Seiko is trolling the market with the TransOcean's flat sapphire. Certainly not everything they do makes sense but the dive watch crystals have been explained adequately by one Tokunaga San to suit me.
Regrettably if I'm correct on the subtleties of crystal properties apart from material I may have inadvertently contributed to the early and untimely death of your wallet. I'm not saying that dual curved mineral is better than dual curved sapphire - it isn't. But dual curved sapphire will kick you right in the wallet. Offering a choice between dual curve mineral and flat sapphire strikes me as reasonable. You pays your money and takes your pick.