I think you'll find their overlords have trained them to say the 'just' part to annoy the customers a bit, but not enough to stop them coming back.They have to start that early to make time for all their smoko, morning tea, lunch, arvo tea breaks and still knock off by 4pm!
LTIH: when the cashier (usually the younger ones) say “that’s just $5.50” . Drop the fucking ‘just’! It’s not necessary and with current prices and n most things, not ‘just’ified!