The supermarkets also dominate the possibility retail landscape so suppliers / manufacturers have no real option but to sell to them.I'm sure there is some profiteering going on, but it's not quite that simple. Supermarket brands have such a low margin for manufacturers (often below or at cost) that they need to increase the margin on their own brands to compensate for the loss of margin.
The way it works is a supermarket approaches the company and tell them "make me x product for y pence per unit" and I can tell you from experience that it is almost impossible to meet the required pricepoint, but if you don't do it, your competitors will.
So because you are making zero margin on supermarket brands, you simply have to make the margin on your own branded products.
It's not new, been happening the last 25 years at least, but it becomes more noticeable in times of crisis.
Food tsar blames shortages on UK’s ‘weird supermarket culture’
Henry Dimbleby says suppliers struggling with rising costs while locked into fixed-price contracts
For anyobe intersted its also worth nosing through a few books, albeit old now, but still a good analysis of market failure and the food and supply chain - Tescopoly, Not on the Label, and Captive State: the corporate takeover of Britain.
