Comparing a straightforward percentage discount against a cashback offer, a bundle deal, or a gift-with-purchase promotion is harder than it sounds, because each format expresses its value differently. Without converting them to a common measure, it is easy to choose the offer that sounds most generous rather than the one that actually saves the most, especially when several retailers present competing versions of a similar purchase at the same time.
The most reliable way to compare dissimilar offers is to reduce each one to a single number: the final amount actually paid, adjusted for the realistic value of anything received in return. A percentage discount converts directly. Cashback should be counted at a reduced value to reflect that it arrives later and depends on a claim being processed successfully. A free item included in a bundle should be valued at what it would genuinely be worth to the buyer, not at its listed retail price.
A few habits consistently distort this kind of comparison and are worth checking for deliberately.
In practice, this comparison doesn't need to be exact to be useful. Rough estimates of final cost, adjusted honestly for delay and uncertainty, are usually enough to reveal which of several offers is genuinely better, even when their formats are completely different from one another. Writing the rough numbers down side by side, rather than comparing them from memory, also makes it much easier to spot when an apparently smaller discount is actually the stronger offer.
Offers are easiest to compare once they are translated into the same terms: what will actually be paid, and what will actually be received, once every condition is accounted for. An offer that looks smaller on paper but is simpler and more certain often beats one that looks larger but depends on several things going right.