Amazon offers the used Fujifilm Instax Mini Instant Film Twin Pack for $7.62 with free shipping. That's $8 under a brand new box and the lowest total price we could find. It includes 20 film sheets for Instax Mini cameras that develop similarly to a Polaroid.

Of note, this item comes in "Very Good" condition in the original packaging, but the packaging my be damaged. "Like New" condition is also available for a few cents more. No warranty information is provided.