They embed rfid tags into their price tag labels. Do a search for rain rfid or 900Mhz rfid.
These tags are very cheap ~1cent per and can be embedded directly into the clothes stitching.
These tags are very cheap ~1cent per and can be embedded directly into the clothes stitching.
“I’ll explain later, dear.”
I also wrote a prescient short story, titled "Smart Furniture", published 20+ years ago, where the protagonist's day job was driving past people's houses to scan the tags on the interior, and he considered himself "better" than those folks who stood around in malls scanning the clothing of people as they pass by and accosting them with special offers. The ultimate form of "browser fingerprinting" in a way.
Google themselves has ad offerings making this fairly easy.