The "Free" Trap: Why Your Fallowfield Kitchen is Full of Regret

 

Figure 1: Supermarket “Buy One Get One Free” (BOGOF) promotion using prominent yellow price framing.

Source: Google Images (2026), search term “BOGOF supermarket UK”.

 

The Hook

Imagine it is a rainy Wednesday evening in Manchester. You walk into the Wilmslow Road Lidl needing only one thing. But a shiny yellow sign intercepts you with a Buy One Get One Free (BOGOF) offer. Minutes later, you are at the till with two packs of pasta, a higher total bill, and a sense of confusion. This everyday scenario reflects a national issue. In the UK, supermarkets are facing intense pressure from environmental charities like WRAP to cancel BOGOF deals, which are blamed for contributing to 10.7 million tonnes of national waste (WRAP, 2023). Why do we keep falling for it? The answer lies at the intersection of microeconomics and human psychology.

 

The Rational Baseline

To understand why we fall for these deals, we must look at the traditional economic benchmark for human behaviour. In standard microeconomic theory, we assume that consumers are rational agents, sometimes nicknamed Homo Economicus (Varian, 2014). This version of a human acts like a logical computer that only cares about marginal utility, which is extra satisfaction gained from consuming one more unit of a product.

When this rational robot sees a BOGOF sign, they do not see a gift. They see a mathematical requirement to buy two units at a 50% discount each. If they only need one pack of pasta for dinner, the second free bag has zero marginal utility to them. Because the rational agent is perfectly efficient, they would rather pay the lower price for a single bag than spend more money to get two. They are immune to marketing tricks because they focus strictly on their actual needs and the unit price.

 

The Realisation: Why Free is a Psychological Magnet

However, most of us do not shop like robots. Behavioural economics teaches us that humans have bounded rationality, meaning our decision-making is limited by our emotions. This is where the zero price effect comes into play. This is systematic bias, where the presence of a free option completely distorts our ability to think clearly.

When a price drops to zero, it is no longer just a low price. It becomes an emotional trigger. As Dan Ariely (2008) explains, "free" creates an emotional charge that makes us perceive the benefits of an item as much higher than they truly are. In a famous experiment, consumers were offered a choice between a high-quality Lindt truffle and a cheaper Hershey's Kiss. When both had a price, most chose the Lindt. But the moment the Hershey's Kiss became free, the majority switched — even though the price difference between the two remained exactly the same (Shampanier, Mazar and Ariely, 2007). "Free" is a psychological magnet that overrides original consumer preferences. In the context of BOGOF, our brains stop calculating the actual cost and start focusing on the excitement of receiving a gift.

Weaponising the Trigger: The Art of the Frame

All of this depends on how promotional offers are packaged, which is a concept known as the framing effect. Nobel laureate Daniel Kahneman (2011) notes our brain operates at two speeds, including the fast, impulsive System 1 and the slow, meticulous System 2. Imagine you are in a supermarket. A 50% off sign on the pasta forces your brain to do the maths and activates your System 2, which asks if you actually want to spend money on this right now. However, a BOGOF feels completely different. It is framed as a pure, shiny gift.

By framing the second bag as a gift, the supermarket slips right past your rational defences. Once the offer is framed as a guaranteed win, another trap emerges called loss aversion. Behavioural economics tells us that the pain of losing something is roughly twice as much as the joy of getting it (Kahneman and Tversky, 1979). You feel you are “losing” a free gift if you walk away. Once placed in your trolley, the endowment effect kicks in, creating a sense of psychological ownership that makes it nearly impossible to put back (Kahneman, Knetsch and Thaler, 1990).

 

The Hangover: Why Your Gift is a Global Problem

When that extra bag of pasta sits in your cupboard for a year, it stops being a personal bargain and starts being an economic disaster. In a perfect world, resources are only used to make things that people actually value, which is known as allocative efficiency. However, the free trap creates a massive market failure because it tricks us into taking goods we do not actually need.

This impulsive shopping creates a negative externality. While the supermarket makes a profit and you feel a temporary win, society bears the hidden costs of the water, energy, and labour used to produce, pack, and ship that wasted pasta. This stems from asymmetric information (Akerlof, 1970); the retailer understands your psychological biases better than you do, using that information to clear stock at your (and the environment’s) expense. This leads to deadweight welfare loss, where the “gift” reduces the total well-being of society.

The conclusion

So, how can we escape the BOGOF trap? The key is learning to de-bias our brain before our impulsive System 1 takes over. Next time you see the shiny yellow sign in the shop, ask whether you would still buy two if it were simply half-price. If the answer is no, leave it on the shelf. 

Figure 2: SU Essentials at the University of Manchester

Source: University of Manchester Students' Union (n.d.) essentials Available at: https://manchesterstudentsunion.com/essentials/the-pantry (Accessed: 17 April 2026)

 

Wait, what about when "Free" is actually for a good cause? Programmes like the SU Essentials at the University of Manchester offer free groceries to support students through the cost-of-living crisis. While this is a vital financial lifeline, does the zero price effect still lurk in the background? Even when items are provided by the SU, could the lack of a price tag encourage us to take that extra tin of beans "just because it's free," potentially leading to more waste in our shared kitchens? It is a tricky balance, but by being mindful of our own biases, we can ensure these great initiatives help our wallets without hurting the environment. By making conscious choices, you stop funding deadweight loss and cast a vote against those 10.7 million tonnes of waste (WRAP, 2023).

Reference List

 

1.     AAkerlof, G. (1970). The Market for Lemons: Quality Uncertainty and the Market Mechanism. The Quarterly Journal of Economics, 84(3), pp.488-500.

Ariely, D. (2008). Predictably Irrational: The Hidden Forces That Shape Our Decisions. New York: HarperCollins.

Kahneman, D. (2011). Thinking, Fast and Slow. London: Penguin Books.

Kahneman, D., Knetsch, J.L. and Thaler, R.H. (1990). Experimental Tests of the Endowment Effect and the Coase Theorem. Journal of Political Economy, 98(6), pp.1325-1348.

Kahneman, D. and Tversky, A. (1979). Prospect Theory: An Analysis of Decision under Risk. Econometrica, 47(2), pp.263-291.

Shampanier, K., Mazar, N. and Ariely, D. (2007). Zero as a Special Price: The True Value of Free Products. Marketing Science, 26(6), pp.742-757.

Varian, H.R. (2014). Intermediate Microeconomics: A Modern Approach. 9th ed. New York: W.W. Norton & Company.

WRAP (2023). Food surplus and waste in the UK – key facts. Available at: https://www.wrap.ngo/resources/report/uk-food-waste-food-surplus-key-facts (Accessed: 10 April 2026).