It's no surprise that the likes of Aldi and Lidl can sell you a chunk of cheese or a Christmas turkey at a lower price than Waitrose or Sainsbury's.
But did you know that the budget supermarket's version often comes from the same supplier - even, sometimes, the same farm?
An investigation by the Sunday Mirror has revealed that, for example, Waitrose's Christmas Freshly Crumbed Smooth Stilton Jar costs £6, while Lidl's Long Clawson Blue Stilton ceramic pot costs just £3.79.
Both are made at the Long Clawson dairy in Leicestershire - and the Lidl pot is actually larger, making it not much more than half the price.
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Meanwhile, a two-pack of H Forman & Son smoked salmon with gin and tonic costs £11.99 from Selfridge's food hall, but just £7.98 from Aldi; and 100g of mixed charcuterie from Woodall's costs £6.95 at Harrods but only £2.97 from Aldi.
In some cases, there are differences between the products. Turkey hatchlings produced at Kellys Turkeys in East Anglia go on to be worth £12.99 per kilo when reared by Kellys themselves.
"Many shoppers are unaware they are spending more than they should," comments Tony Baines, Aldi's joint managing director of corporate buying.
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"At Aldi many of our products are sourced from exactly the same suppliers as more expensive food retailers."
This year, according to retail experts, the cost of Christmas dinner is likely to be lower than ever, with both Morrisons and Asda cutting thousands of prices.
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If you're prepared to shop around, says Good Housekeeping, it's possible to feed eight people for just £2.48 a head. If you're not, then Aldi is your best bet, coming in at £2.75 per person.
Lidl and Iceland are the next cheapest, with their Christmas dinner ingredients coming in at £3.07 and £3.10 respectively.
However, with Brexit looming and already hitting exchange rates hard, shoppers are being urged to make the most of low prices - so eat, drink and be merry while you can.
As retailers move into a new ordering cycle, the costs of imported finished products, raw ingredients and transport will all rise, putting pressure on retailers to hike prices.