There is miminal cost to the business when a customer in a shop puts something in a trolley and then changes their mind

Not if some of the items were from the frozen food isle lol

There are also staff costs for putting it back on the shelves, if indeed that can be done, chilled food would presumably be dumped as the store would have no idea it had been out of the chilled food cabinet.

In a clothing store assistants spend hours rehanging and refolding clothes that the buyer has decided not to buy, all added costs.