Unless someone pops up with a production pair of glasses, id say they were knock offs of the Ray Bans used in the film. Back in the 80's, and considering where They Live was filmed, knock off's were all over LA's Chinatown as well as every swap meet you could find, gas station, super market, liqueur store... Considering they had at least two boxes of them on camera knock off's would be cost effective as well as not needing any product placement clearance. In other words why spend $30 on something you can get for $3 en mass.