A discount can feel persuasive even when the amount saved is small or the original price is hard to judge.
A percentage off can make a purchase feel like a decision that has already been made for us. The offer is limited, the saving is framed prominently, and the full price becomes the reference point. I can find myself thinking about the discount before asking whether I wanted the thing at all.
The numbers matter, but so does the presentation. Saving ten percent on something useful is different from spending money because a countdown suggests the chance will disappear. A bargain is only a bargain relative to what I would otherwise have done.