A large discount can be less valuable than it looks once delivery, subscriptions, accessories, warranties and returns are included. This guide gives you a repeatable UK deal-checking method, with simple calculations, a comparison table and a printable checklist for deciding whether an offer is genuinely cheaper.
Overview
Checking whether a deal is really cheaper means comparing the total cost of getting and using the product, not just the percentage shown beside the sale price. A product marked “was £500, now £399” may be good value, but the headline saving does not tell you whether £399 is a normal price, whether another retailer sells it for less, or whether delivery and required extras change the result.
The same principle applies to supermarket offers, electronics deals, travel bookings, mobile contracts and voucher codes. A discount code can reduce the basket total while a delivery charge cancels out the saving. A cheap monthly plan may cost more over its full minimum term. A multi-buy offer may be poor value if you would not otherwise buy the extra items.
Use this five-part test:
- Identify the exact product, service or basket being compared.
- Check its recent price history or ordinary selling prices.
- Calculate the complete purchase cost.
- Compare like for like with other retailers or plans.
- Check the practical terms, including returns, warranty and any recurring commitment.
For broader comparisons, you can pair this method with our guide to TV deals in the UK, cheap laptop deals or supermarket basket comparisons.
How to estimate the real cost of a deal
1. Record the exact offer
Write down the brand, model number, size, colour, storage capacity, specification and included accessories. Small differences can make two apparently identical deals unsuitable for direct comparison. For services, record the monthly price, contract length, setup charge, usage allowance and whether the price can change during the term.
Save the offer page or note the date and time you checked it. This is useful when a promotion has a countdown timer, limited stock message or changing basket price.
2. Check the price history
A price-history checker can show whether the current figure is unusual, but treat any result as evidence rather than a guarantee. Check that the history relates to the same model and condition, and notice whether it includes marketplace sellers, refurbished stock or temporary pricing.
If a dedicated checker is not available, manually compare the retailer’s current price with other reputable listings and look for the product at different points in the retailer’s own sale cycle. Search by model number rather than a broad product name. A “50% off” label is less useful if the previous price was rarely charged or if a newer version is available for a similar amount.
3. Calculate the all-in price
Use this basic formula:
Real purchase cost = item price − genuine discounts + delivery + compulsory extras + unavoidable fees
For a subscription or contract, calculate the full commitment:
Total contract cost = upfront charges + (monthly charge × number of required months) + compulsory add-ons
Then subtract only discounts you can realistically use. For example, do not count a voucher code if it excludes the item you want, requires a minimum spend you would not otherwise make, or applies only to a first order you have already used.
4. Compare the useful unit price
For groceries and household products, compare price per kilogram, litre, item, wash, sheet or serving where appropriate. A larger pack is not automatically cheaper, and a multi-buy offer is not a saving if part of it goes unused. Include delivery or collection charges when comparing supermarket baskets. Our grocery savings tracker guide can help you organise this type of comparison.
5. Check value beyond the ticket price
Consider what you receive for the money: delivery speed, installation, customer support, included accessories, warranty arrangements, energy use, repairability and return convenience. For travel, include baggage, seat selection, transfers, resort fees or other required extras. For broadband and SIM-only deals, compare allowances, network coverage for your location and the price after any introductory period. See our SIM-only comparison guide and contract renewal guide for a structured approach.
Inputs and assumptions
A reliable comparison depends on using the same assumptions for every option. Before calculating, decide:
- Quantity: Are you comparing one item, a full basket or the amount you actually need?
- Condition: Are all options new, refurbished, used or clearance stock?
- Delivery: Will you pay for delivery, collection, installation or returns?
- Discount eligibility: Can you genuinely use a student discount, NHS discount, loyalty offer, cashback rate or promotional code?
- Time period: For contracts, how long will you keep the service?
- Risk and convenience: Is a slightly cheaper seller worth a less convenient return process or weaker support?
Separate a cash saving from a value judgement. A £20 lower price is a cash saving; free installation, faster delivery or a longer included warranty may affect value but should not be presented as the same thing. Also distinguish between money you would have spent and money you were persuaded to spend. Buying an unnecessary item for £30 instead of £40 is not a £10 saving if the purchase was not needed.
Deal comparison table template
| Option | Item or plan price | Delivery and fees | Discounts used | Real total | Key terms |
|---|---|---|---|---|---|
| Retailer A | £___ | £___ | £___ | £___ | ___ |
| Retailer B | £___ | £___ | £___ | £___ | ___ |
| Retailer C | £___ | £___ | £___ | £___ | ___ |
Fill in the table before choosing. It prevents a large headline discount from dominating the decision when another option has a lower final total.
Worked examples
Example 1: an electronics discount
Suppose a retailer lists a laptop at £620 and offers a £40 code. Delivery is £8 unless the basket reaches a stated threshold. The real cost is £588: £620 − £40 + £8. A competing retailer lists the same model at £599 with free delivery. The first offer saves £11 against that alternative, but only if the code applies and no compulsory accessory is required.
Now compare like for like: storage, memory, processor, operating system, delivery time and return terms. If the £599 model includes an accessory you would otherwise buy, record that separately as additional value rather than quietly reducing the laptop’s cash price.
Example 2: a multi-buy household offer
A two-pack costs £9, while one pack costs £5. The two-pack is cheaper per pack at £4.50, but it is only the better purchase if both packs will be used before they become unsuitable or take up unwanted storage. If delivery adds £3 to the order, compare the complete basket total, not just the displayed pack price.
Example 3: an introductory service price
A service costs £18 per month for six months, followed by £30 per month for six months, with a £15 setup fee. The 12-month total is £303: (£18 × 6) + (£30 × 6) + £15. Comparing only the first monthly figure would understate the commitment. If another plan costs £25 per month with no setup fee, its 12-month total is £300, before considering differences in allowance, coverage or support.
When to recalculate
Recheck the deal whenever an input changes, rather than relying on an old comparison. Recalculate when:
- the retailer changes the item price, voucher code or delivery threshold;
- the promotion moves from an introductory rate to a standard rate;
- stock changes from new to refurbished, marketplace or clearance condition;
- you add or remove an accessory, baggage option, installation service or protection plan;
- a competing retailer changes its price;
- you are shopping around a major sales period such as Black Friday, Boxing Day or a seasonal clearance event;
- your quantity, travel dates, usage needs or contract length changes.
Use this quick checklist before paying:
- Have I identified the exact model, size or service allowance?
- Is the current price genuinely competitive with recent or alternative prices?
- Have I included delivery, fees, accessories and compulsory extras?
- Does the voucher or cashback offer definitely apply to my purchase?
- For a contract, have I calculated the full minimum-term cost?
- Have I compared the same specification, quantity and condition elsewhere?
- Would I still buy it without the countdown timer or “was” price?
- Are the returns, warranty and cancellation terms acceptable?
If the answers are clear, you have a stronger basis for deciding whether the offer is genuinely cheaper. If not, pause and compare again later. Our guides to stacking UK discounts and finding better UK travel deals can help with the next stage, but the same rule applies: calculate the final cost before treating a promotion as a saving.
