With orders of $25 or more, Amazon offers the Tampax Pearl Plastic Tampon 50-Pack for $9.27. Clip the $4.50 off coupon on the product page to drop the price to $4.77. Plus, Prime members receive free shipping. That's at least $5 less than you'd spend at a local retail store. This pack includes 30 regular, 10 super, and 10 lite tampons.
Note: This item is offered as part of Amazon's "add-on program" and can only be purchased with an order of $25 or more.