Well, I agree with what has been said here.
I can't speak to the QC issues as I have personally only seen beautiful pieces (I don't own any of the helmets mentioned.)
The Christie's auction certainly had an effect: it sapped the budgets of those with deeper pockets and drove prices up on specific items (seen a TOS MR phaser on eBay lately? $800 - $2000..)
Also, with a dip in fandom (the lull is certainly upon us) and with the rising prices of these pieces, less can afford them.
Added to that, the "biggies" have been done. Okay, there must be a big audience for a Vader helmet, but there are also a million of them, starting at Toys R Us and they have been available since, what, the 1978 Don Post?
(maybe that was even late 1977? can't remember.)
So, yeah, I'd love a phaser and a Han Solo blaster, and Luke's Lightsaber, but when it gets down to Jango Fett's left boot-dart-quiver, uh, no thanks.
Plus, it's going to cost $799 or something.
After a while you feel like the people making these are (as ever) pushing the prices up to the very highest mark, which will also reduce the available market.
I don't want to say "gouging" because they get what they can for these pieces, but when the prices get as high as they are now, you will see a much pickier audience ("QC issues") a smaller audience (who can afford it?) and the items have to be pivotal (Enterprise, Millenium Falcon - yes.) and iconic to justify the cost.
I suspect MR has seen this trend and knows exactly what it is doing, when it tries to do a "CE" program, and gets bought by Corgi (phew, just in time, no doubt.)
They have milked the market and unless there are some other big collector properties, they may have passed their summit of sales.
Another sign of their awareness of this is the attempt to re-issue pieces at a lower price point, which only backfires (IMHO) because they already got the die-hard collector money and now those people will feel "cheated" that they bought a limited edition only to have copies coming out and probably not terribly different to the casual observer, taking away from how special their big ticket purchase was.
On the other hand, making them from "less exotic materials" sounds like they will be cheap castings of the original out of pot metal (for those who would otherwise jump at the "second chance" to get one.)
So in a collector's circle, people don't want to be labelled as the "second tier" buyer of the "cheap knock-off"
nor the person who paid too much for what is perceived to be a common prop replica.
I belive the only way to do this multiple tier of lmited editions is to do it like the DVD (still maddening) but offer the "better" version later for a premium.
As a collector this is mostly infuriating because it works. If I got one at a decent price and then one comes out that is better in a significant way, I would want to "upgrade" - selling my previous purchase and buying the new one.
My other opinion (are you sorry you asked now?) about helmets is that, if you can't wear them, they better be pretty inexpensive. If people can wear their beautiful Rocketeer helmet to a convention and show it off, they get some positive reinforcement for their high dollar purchase. Likewise, if they are "trooping" or Vader in public, some will want the very best for it and if it (inevitably) get a little beat up in the process, they may just buy another.
However, if it's the headgear of the third Gungan to the left in scene 63 of Phantom Menace, then they are only going to sell 13 of them no matter what.
Holy cow, did I ramble. Sorry about that Chief.
:rolleyes
) 
