[thinking out loud]I wonder if it's possible to retrocoat resin filters by taking them to an optician who makes their own spec lenses on site? I know they do some coatings (tints, scratch resistance) but unsure if they do the sort that we (as photographers) might find useful (anti reflection being the main one). Anyone here work in a lab that makes spec lenses or have a mate who does so?[/thinking out loud]
I've spoken to Lee about coating and they said it's difficult considering the large area invloved so big increase in cost made even bigger by the inevitably high reject rate, and at the end of the day only marginal benefit.
I tend to agree. Flare shouldn't be too serious if you avoid stacking whenever possible in difficult situations, and ghosting - always a problem with filters regardless - can usually be worked around. Eg, with a sunset, don't position the sun right in the middle.
The two things that make Lee expensive are a) quality, and b) quality control. I've tested a lot of filters and grads and with most others the colour varies a bit, the grads lines are not so consistently hard/soft, and there are occasional sharpness issues.
If you buy a set of Lee grads, they will all be exactly to spec, and if you need to replace one, it will also be the same. It seems that the best way to ensure this consistently high standard of quality involves a lot of costly manual work.
BTW, it's only necessary to have a light-tight seal around the filter with the Big Stopper and other extremely dark NDs.
Edit: having said that, it rather depends on how keen a grad user you are. If you've got a set of three or four, then consistency of colour and grad lines etc is very important. I'm not a great fan of grads (prefer HDR blending) but like a lot of folks I do have just one! It's a Kood, it works just fine, and you would not be able to distinguish a shot taken with that vs Lee.