Do I need to keep the purple items?

Any other purpose for the purple item other than exchange for other weapon/item? Cause it seems that buying from market is easier than collecting things to exhange them. Btw been playing this game for 2 weeks.

Any other purpose for the purple item other than exchange for other weapon/item? Cause it seems that buying from market is easier than collecting things to exhange them. Btw been playing this game for 2 weeks.