Yeah it's kind of a grey area. Generally studios look the other way if there isn't already a licensed replica out on the market but others will send a cease & desist just to protect their intellectual property.
I've had 2 notices since starting to sell replicas: 1 from Lionsgate for Orange is the New Black ID badges and 1 from 20th Century Fox for Paper Street Soap Co. business cards from Fight Club.
The good news is that most studios will simply send you a notice to stop selling the prop and that's the end of it as long as you comply. I just pulled my listings on my Etsy and that was the end of it. You'll only get sued if you don't oblige to the warning.