I have to think the scrutiny for costumes and helmets is much higher than for display pieces. There is lots of potential for lawsuits regarding safety of products intended to be worn. This may also affect decisions made that hurt screen accuracy.
Not sure I agree. I believe the scrutiny for display pieces is higher - they're meant to be viewed/studied.
How many people troop in a costume with an SL or TM Vader lid? I'm not even sure I'd troop/costume with an EFX Legend.
Now a Darth Ugly or a EFX PCR, sure. They're accurate enough, less expensive, and easily replaceable.