Jeff has some bitcoin on a mobile wallet.
Jeff wants to buy a PC game with his bitcoin.
The retailer accepts lightning payments but Jeff doesn't have any channels open yet.
The retailer offers an option to open a channel with his first purchase.
"Pay with bitcoin and all future payments will be [nearly] instant and free."
The retailer has other channels open to major hubs.
Jeff can now use his LN funds anywhere LN is accepted and it cost him NOTHING.