The $.50 is $.50 regardless of what the voucher is for. It provides exactly $.50 no matter what. Sure, maybe someone with $700 at the ready for a laptop won't be the kind to be clipping $.50 coupons for anything but the same tendency to consider percentages rather than absolute values remains regardless of actual numbers. People will pat themselves on the back for saving $10 on a $50 garment but won't bother going out of their way to save $100 on a $20000 car.