Polaroid 600 instant film are no longer in production. But there are still those old 600 Polaroid film out there are camera stories which might be already expired. But expired doesn't mean you can't use those Polaroid 600 film unless battery is dead or chemicals are coming out. Biggest problem is the price. Each Polaroid 600 exposure cost you $4 - $5 which is way too expensive. Also it hurts more since not all of these exposure would work. Some gonna come out blank.
So All Polaroid 600 instant camera owners search for cheaper alternative for Polaroid 600 instant film. But there is only one alternative for Polaroid 600 film and that is 600 instant film which is made by The impossible project.
They have 2 types of type 600 instant film. The Impossible Project PX 600 Silver Shade UV+ and PX 600 Silver Shade Monochrome Instant Film. You can buy both of these types of type 600 instant film from their own site and Amazon.com. These 600 instant film have 8 exposures in a pack and a pack cost you like 25$. So each will cost you like $3. That's the cheapest alternative for Polaroid 600 instant film you can find.