Kmart offers the HP Multipurpose 20-lb. 8.5x11" 500-Count Paper Ream, model no. HEW112000, for $10.99. Plus, Shop Your Way Rewards members can add two reams to cart for $21.98 to earn around $22 in SYWR Points. (Not a member? It's free to join.) With $11.79 for shipping, and assuming you'll use the credit, that's the lowest total price we could find for this quantity by $6. It features 96 brightness.
Of note, Shop Your Way Rewards members will earn a Kmart credit with this purchase and may be eligible for additional credits and discounts.