You might think you're displaying savvy shopping techniques by sticking to supermarket own brands, but if you reach for the items without checking prices, the chances are that you've seen the cost of some items in your trolley rise by up to 50%.
So what's going on?
A report by The Grocer, has found that the prices of supermarket own brands are going through the roof.
It said that some supermarkets have increased the price of more than 40% of their own brand range. At Tesco, over 43% had gone up in price (although 28% had fallen in price). At Sainsbury's 41% had risen in price, and 37% had fallen in price. Only Asda had lowered more prices than they had increased.
Tesco and Sainsbury's told The Grocer that they were doing everything possible to keep costs down, but in some instances they had needed to put up some prices because of the rising costs of production.
Elinor Zuke, a journalist with The Grocer, told AOL: "Commodity price inflation is the problem. You can't get around the fact that animal feed is getting more expensive, and the cost of distribution is rising."
Price risesThis matches the research from the British Retail Consortium, which found that food price rises have been accelerating towards the end of the year.
Stephen Robertson, British Retail Consortium Director General, said: "Costs for commodities such as wheat and corn have eased off since peaking earlier in the year but these pressures, coupled with the impact of poor harvests, are continuing to filter through to fresh foods, with meat, fish and vegetables hit particularly hard."
The Department for Environment, Food and Rural Affairs says that this is just the latest piece of bad news in a long line, as food prices have risen 12% in real terms over the last five years - taking us back to 1997 in terms of cost of food relative to other goods.
And the trend is unlikely to change any time soon. The Grocer concluded that the cost of the weekly shop was likely to rise at least 4% a year for the next decade at least. Zuke said: "A lot of it is dependent on the weather, but we will at least have to wait until next year when the current crop is harvested before there's a hope of prices coming down, and even then we don't know that they will because we don't know what that harvest will be like"
Of course, this doesn't mean we ought to shun own brands, as costs have risen across the board. Zuke says savvy shoppers are increasingly buying own brands, which now appear in 80% of all Tesco trolleys and 72% of those at Sainsbury's. She adds that all the supermarkets are increasing their range of 'lower budget ' food by an average of 20% - which shows we are pulling out all the stops to cut costs.
However, these findings serve as a useful reminder that any shopping-by-habit can be risky. It's worth taking the time every-so-often to check the alternatives, to ensure that the products that were the cheapest last time remain so now.