A product page is the beginning of a price comparison, not its conclusion. Two stores can display the same number and ask for different amounts once you select a size, enter an address and choose delivery. The useful question is how much each acceptable order will cost when it is ready to place.
Start by fixing the product specification. Record the model number, color, size, quantity and included accessories. A comparison between different package sizes or versions may still be worthwhile, but label that difference clearly. Otherwise, you can mistake a smaller package for a better offer and only notice after delivery.
Open a basket at each plausible seller and enter the actual destination. Add the item price, delivery and any unavoidable charges displayed for that order. Apply a discount only if the checkout accepts it and you meet its conditions. A banner promising a reduction is not the same as a reduction in the amount payable. Keep the payment method consistent when different methods produce different totals.
Use a short note with one line per store. Include the complete total, delivery estimate, seller identity and any important exclusion. There is no need to copy the whole listing. The note should make the deciding differences visible without requiring another tour through several tabs. Record when you checked because a saved comparison is a snapshot, not a promise that the offer will remain available.
Consider a hypothetical order in which Store A has the lower product price but charges for delivery, while Store B includes delivery. Compare the two completed amounts directly. If Store A asks you to add an unwanted accessory to qualify for free shipping, calculate that revised basket separately. The accessory is a new expense, even if the delivery line becomes zero.
Price does not have to be the only deciding factor. An order that arrives before a genuine deadline or has a clearer return process may justify a higher total. State what the extra amount buys. If you cannot identify a practical benefit, the more expensive offer needs a stronger reason than a familiar logo or an attractive countdown.
Before confirming, inspect quantity, variation, seller and shipping option once more. Check that an optional extra has not entered the basket during the process. Save the final summary and compare it with the order confirmation. Keeping that small record makes it easier to explain a discrepancy and gives your next comparison a useful starting point.