Amazon offers its Prime members the Post-it 1" Durable IndexTabs, model no. 686-PGO, for $5.67. Clip the coupon on the product page to drop it to $3.67. With free shipping, that's the lowest total price we could find by $2. (Non-members can get free shipping with orders of $25 or more; otherwise, shipping adds $5.58.) It includes 66 tabs.

Amazon Prime membership is $79 per year; however, Prime is free for college students for six months, and free for parents and caregivers for three months.