They are all the same, all they want is your money, the products all come from the same factories, suppliers, just a different packet. They all squeeze the life out of suppliers,producers to get the prices as low as possible.
Just happens that Tesco has had a dominant model for years,and has sat on its laurels for to long,and has been taking a kicking from all comers and is now playing catchup.
Not sure. I'm not defending Tesco, but often in Wales there will be a special offer of Welsh Lamb that is way WAY below anything that you will see in any other Tesco or even local butcher. I really do think that they sometimes source locally, but does the supplier get really screwed ? Delicious welsh lamb at £8.50 per kilo, I can't believe the supplier is making much 
I worked for a haulage company a few years ago that had a good contract with Sainsbury's. I was picking up a load of pork chops at an abbotoir one day and one of the fellas told me that Sainsburys wanted to run a 2 for 1 promotion on pork chops and were expecting the meat company to supply the extra chop free of charge!!

The directors of the meat company were refusing but Sainsburys were playing hardball and threatening to take their business elsewhere. Apparently the meat company were between a rock and a hard place as they depended on the Sainsburys contract, but would make a loss if they supplied the extra meat for free..... 
All two for one promotions of BOGOF's if you prefer are at the expense of the supplier.
It's not the supermarkets who are taking the hit. They are not that benevolent. 
Yes Opti, that is usual practice. However it is often the supplier who encourages that as they want maximum distribution for their product whilst lowering the unit cost of production by greater quantities coming off the lines. Certainly the manufacturers I negotiated with often offered me and other buyers a lower unit price if we purchased say 100,000 units instead of 80,000 with promotions like BOGOF's attached. If at the end of the year we got close to meeting the next price discount level by buying another 15,000 units that could be worth to us the retailer another £50,000 of gross profit in just terms of a further discount on the cost price on all our buying from that manufacture for the year. It is all a big game; you as a retailer want to sell product that suits your business model, but at the right price to encourage consumers to buy; the manufacturer wants to increase it's levels of production and increase product distribution to lower the manufacturing costs and improve the market share of their line. Higher profits,
the name of the game, is the result!
Then, at the end of the day if the price is right and the product has maximum availability, great advertising, the consumer should buy and want more; everyone is happy!
If everyone gets it wrong, with the wrong product, at the wrong price, in the wrong quantities, with poor advertising, you have a turkey on your hands and the retailer with the manufacturer takes a hit!
Product positioning in the market is so important and the manufacturer and retailer all play their part in the profits game. In 2014 the quality, premium products, are being squeezed by the less recognisable and economy / cheaper ones with the supermarkets identified for selling the latter gaining ground and knocking the likes of Tesco for six. The market is a changing and be ready for some fall out as has been seen in the recent past. Morrison's losing market share due to not entering the on-line business until almost too late is yet another example of how a retailer, no matter how big they may be, can lose focus on the market, fail to respond due to an out-dated business model, can come a cropper!