It's for theft. Bad guys/gals are very sneaky these days. Big-ticket items like HDTVs, laptops, etc. are often stolen through subtler means. You can buy a low-end 65" Samsung HDTV for $500. A high-end Samsung HDTV might sell for $3,500. Clever thieves will print out a copy of the UPC sticker for the $500 one and slap it over the original UPC sticker on the $3,500 set. They take the $3,500 to a self-checkout, scan the fake UPC code, get their receipt, show it to the exit police and wander off with a set worth seven times what they paid. The exit police these days are trained to match up the model number, but if things are busy they may not do so. The thieves may even print up a fake model number and display it on the set for the exit police. Stores lose a lot of money through this type of scam. They often don't even know it happened for weeks/months afterward when they're checking inventory and find out they have a lot of the $500 sets but none of the $3500 sets despite records showing the $500 sets were sold out.
Swapping the UPC codes has become a fairly common scheme for higher ticket items. The thieves "buy" something and pay what they're told to pay and get their receipt. Unless the exit police are on their toes, it can work very well. Best Buy has (well had the last time I was there) some of the most diligent exit police who checked everything like mad to ensure it doesn't happen to them.
Fly!!! Eagles!!! Fly!!!