... and not only the "bargains", things with price labels different to that charged at the till.
I've noticed in recent years that down-marked price labels in particular don't always match those charged at the till in some grocery stores (parts of large chains, for example SPAR). These are sometimes known as "convenience" stores, to whose benefit I wonder sometimes. In a recent example, a printed discount label for an item showed a shelf price of £2.00, but I was charged the original price of £2.50 (shown on the receipt). When I queried this, saying a similar thing had happened many times before in that store, I was told that it was up to the customer to check that they were charged the correct amount! The story has often been - "there's a problem with the computer", "it's not updating properly" or something similar. Stated discounts for multiple buys are sometimes not applied.
I expect this could be a widespread practice, but I haven't noticed problems with larger stores, maybe they can afford better "computers". One day I may spend an hour or two filling out the rather large Trading Standards report form. In a recent purchase at a Londis store I was overcharged at the till for a loaf of bread. When I pointed out the discrepancy the assistant smiled sweetly and said that's what it says on the till, didn't offer a refund, thus breaking trading law - training required?
It's obvious to me that in most cases this is not a genuine mistake. For one thing the price at the till is always higher than that marked in my experience. It's organised theft. The shops rely on customers not counting up their bill, and even if they do not wanting to quibble and hold up the queue or create a fuss. Customers could be especially vulnerable at petrol stations for one example.
PS: I just heard a whisper that I'm not "one of the best" customers of a store with poor price labelling and charging co-ordination performance. So to be "one of the best" customers one has to behave in what manner I wonder. Probably to not notice or complain about pricing discrepancies would help. Not wishing to be a sub standard customer I'll avoid this store.
Update 13 Feb 2017:
An example of what can happen reported by the BBC (I haven't noticed a problem with this store chain myself):
Tesco customers overcharged by out-of-date offers
As of 14 Feb the above article has 845 comments, some criticising the BBC for pointing this out (shareholders I guess). It's not just Tesco of course. I first noticed this as a regular occurence in around 2008/9, perhaps it was no co-incidence there was a serious economic downturn at the time.