At Canon, buy one select Photo Paper Pack and get another four packs for free. (Add one pack to your cart; the other four are added automatically.) Even with $5.99 for shipping, they're each at the lowest total price we could find by at least $9, although most are lows by much more significant margins. Sales tax is added where applicable. The available photo paper:

• 5 Canon Photo Paper Plus Semi-Gloss 5x7" Paper 20-Sheet Packs for $9.99
• 5 Canon Photo Paper Plus Semi-Gloss 8x10" Paper 50-Sheet Packs (pictured) for $34.99
• 5 Canon Photo Paper Plus Semi-Gloss 8.5x11" Paper 50-Sheet Packs for $34.99
• 5 Canon Photo Paper Plus Luster 8.5x11" Paper 50-Sheet Packs for $34.99