Buying guide · 10 September 2026
The checkout price is only the first number.
Two products can reverse places on price once you include refills, subscriptions and delivery. Make the comparison over the period you realistically expect to own them.
Use one time period and one currency
Choose a period that matches your decision: perhaps twelve months for a subscription or a few years for a household item. Compare both options over exactly the same period. If one seller prices in another currency, convert the quote and account for the fees your payment provider actually charges. Do not compare a tax-inclusive quote with a tax-exclusive one.
Separate one-off and recurring costs
One-off costs can include shipping, required adapters, installation and an accessory needed to make the item usable. Recurring costs can include replacement filters, refill packs, software subscriptions or consumables. Optional extras should stay optional: include them only if you would buy them.
For an annual subscription, divide the annual charge by twelve for a simple monthly comparison. For consumables, estimate units per year multiplied by the price per unit, then divide by twelve. That monthly average is a planning aid; it is not a prediction of when your card will be charged.
A worked example
Suppose option A costs 60 upfront, 10 for delivery and 8 per month in refills. Option B costs 100 upfront, nothing for delivery and 4 per month. These are hypothetical amounts in the same currency, not prices of real products.
| Cost | Option A | Option B |
|---|---|---|
| Purchase + one-off extras | 70 | 100 |
| Twelve months of recurring costs | 96 | 48 |
| Total | 166 | 148 |
Option B costs 30 more to start but saves 4 each month, so it catches up after 7.5 months. If you only need the item for three months, A costs less under these assumptions. If the two products do different jobs, however, this arithmetic does not make them equivalent.
Read the cancellation and refill terms
Check whether a trial renews automatically, whether there is a minimum commitment, and what cancelling actually stops. A subscription price may depend on a bundle or an introductory offer. For refill-based products, check replacement availability, pack size and delivery costs. A cheap device with hard-to-find consumables can be a poor practical choice.
Keep uncertainty visible
Try a low-use and a high-use estimate. If the preferred option changes between them, your consumption assumption matters more than a small discount. Avoid crediting resale value unless you have a reasonable basis for it. Warranty coverage is not a promise of a particular useful life.
Our calculator uses a deliberately simple formula: upfront price + one-off extras + monthly running cost × months. It does not estimate financing costs, inflation, resale proceeds or reliability. Add known taxes and fees to your own inputs.