The US has a different system with trade in deals.
For a start the prices don't include taxes
Also the deals are part of network provider contracts. So the phones are not bought without a phone contract.
Network operators will subside these deals
Here if you buy the Z Fold 5, you will get the £650. But with a free memory upgrade from 256Gb to 512Gb, this is worth £100
Maybe try looking at deals from network operators to see if they do certain deals as well
They can offer a higher trade in sometimes