No, they are not plastic. My clear covers on my 2000 Audi show no signs of yellowing. However my 92 MX3 does yellow over time. No, they are not made by AMS (why should it matter anyway?). More details on specifics can be found here - [ http://www.300zxclub.com/showpost.php?p=1644761&postcount=51 ] I find it very cumbersome to try to post pics or links here. Cut and past the link and you'll be able to get all of your questions answered if you're already registered on 3ZC. POC (Point of Contact) is Andy Anderson andy93zx@hotmail.com I'll get him to post up on here as well.
Cost has not been determined as of yet since they have not been returned from the manufacturer. ETA of 500 sets from manufacturer is approximately 4 to 5 weeks from now.