I think this was a temporary site glitch and someone else yesterday reported the same problem.
The screenshot you show, is showing 2 very different postage costs on the overview and the actual listing, but today it has corrected itself to a £2.70 postage on both, which the buyer pays.
Your other items all have postage cost, the buyer pays.
I'm using a laptop and Chrome, to view your items.
@snakeyd2