Most foldable/collapsible minimalist luggage that can easily be flattened when not in use?

Hi, I'm looking for the most foldable/collapsible minimalist luggage, both carry-on and suitcase dimensions. I've browsed on Amazon and other sites and am curious about personal experiences here.

Important criteria:

• Durable but flexible material
• Must be able to fold/collapse into a small package and not take up a lot of space when not in use.
• Cool patterns/colors would be nice but not a requirement.
• Optimally under $100.

This stuff looks promising, even if some of the models are pricier: http://www.biaggi.com , has anyone used this? It's not on Amazon so having a harder time finding more candid reviews.

Any leads? As Stephen King would say, thankee.