they may well have some good buys,

, but all they are doing is basicly tricking the public into a false sense of " a good buy" Most , not all simply walk around a supermarket placing items in the trollys not realising what they are paying, this applies especially to fresh goods, meat, fruit veg, salads etc.
How many know the real price when an item like the humple swede is priced at 79p kilo, that makes an average sized swede around 95p - £1 20p each or leeks at £1 89 kilo expensive , compared to a local greengrocer selling at around half that price. yes , they have their offers , buy one get one free, etc, etc, which of course they advertise well......... leading the custy into thinking everything is cheaper, far from it.
Oh and those offers, do you really think they are giving them away

, No chance the grower is paying and losing everytime to the big boys. I have a close friend who used to supply the supermarkets with salads, he would set out a growing plan for these supermarkets, all goes well untill they say , next week we are having a promotion buy 1 celery get 1 free, and you are supply the free one , Yes, hard to believe but true, I hasten to add he no longer supplies them after all the dirty tricks they do.
another example, they got a potato supplier to invest over a million £ in production lines for potatoe supplies, 2 years later they went elswere leaving them in the lurch. I could give you numerous other examples, all they are are monopilies conning the public.
personaly I very very rarly step foot in the places.
geoff