With regards to retailers passing it on, I think this (from This is Money) says it all:
Supermarkets are stinging their customers with bogus special offers, a leading consumer group has claimed.
Which? said Waitrose, Sainsbury's, Marks & Spencer and Tesco had all flouted Government guidelines on sales and promotions.
Introduced in May, the guidelines say an offer is genuine only if it is a discount against a price charged throughout the previous 28 days.
However Which? found a number of promotions failing to comply, including one for Waitrose blueberries. They sold at £3.99 for just two weeks before being offered half price at £1.99.
Gallo wine sold by Sainsbury's at a discount was sold at the higher price for only a week.
And Marks & Spencer cherries were marked as half price at £2.49 even when the full amount had not been charged for a month.
Which? also expressed surprise that Tesco and Marks & Spencer bacon was on 'special offer' for the whole of its three-month investigation.
Nikki Ratcliff, research chief at the consumer watchdog, said: 'We all like a good deal, but special offers encourage us to spend more than we would otherwise and may make us buy food that we throw away.
'Supermarkets need to comply with the spirit of the new Government guidelines and stop misleading consumers into thinking they're getting great deals when they're not.'
Martin Fisher, a trading standards expert who has worked with a number of councils, said: 'The results strongly suggest that there is plenty more work to be done in getting supermarkets to comply with the rules.'
Which? says offers should last no longer than the period in which the higher price was charged. It also said the discounts should be calculated against the preceding price and not against prices from weeks or months before.
It said three-quarters of shoppers seek out special deals and more than half buy products solely because they are knocked down.
A high proportion – 30% - said 'buy one get one free' deals caused them to purchase food which ends up in the bin.
Which? said this contributes to a food waste mountain amounting to 6.7m tons a year.
Households with children waste an average of £610 a year on food they throw away.
Waitrose yesterday promised a review of how it runs special deals. A spokesman said: 'It is never our intention to mislead customers.' Marks & Spencer said: 'We always aim to offer our customers excellent value and follow guidelines on promotions wherever possible.
'For the bacon, unfortunately we made a mistake with the ticketing of this product and we apologise to our customers. We rectified it straight away.'