Staples.com has Vertical Cascading Poly Folders on sale for 70% off! Easy Rewards members get free shipping on all items.  If you are not a member, no problem! Choose the free “ship to store” option.

Staples Cascading Vertical Poly File, Letter Size, 6 pocket (reg $8.99) $2.70, clearance price
Free shipping to Easy Reward members or to your local store
Final Price: $2.70