As far as DP, Rubies and other licensed helmets....
It depends on which helmets you're talking about? If you look at the early Don Post helmets, they were made for the casual costumer (though the '95 will live-on in all our hearts). People didn't want to spend money on an expensive fiberglass cast replica to go to a Halloween party, or to let their kids play Star Wars. Most people wanted a helmet that's not expensive, and just realistic enough for people to look at them and know who it is!
As the popularity of these items grew, so did the quality and accuracy. We had the Deluxe helmet line, then the Rubies and now the wonderful MR's (I can't wait to get my hands on one of these). Will we ever see a direct 1:1 casting, no. You have enough people trying to pass props off as 'screen-used' as it is.
The other issue is quality of a mass-produced item. A TDH member painted a master ESB helmet for a licensed company.....and he knew then that there would be sacrafices in the final version because they were being produced in quantity.
LOL, i know there is no organization to my above response...I'm just typing stuff as it pops in my head!