EXCLUSIVE

Action Bronson just added the "Mona Lisa" of water pipes to his collection and he dropped a ton of cash to get it.

AB picked up his "respiratory recycler" bong -- made by blowing artist AKM -- over the weekend. It took 2 weeks to complete, and the final price tag was $20,000!

Art dealer Marcel Soufan -- who also owns a Tampa smoke shop -- says Action's collection is major. He delivered a Japanese SLOP glass pipe to the rapper just last week ... and estimates Action has stockpiled about $50k worth of super fancy bongs.

Hey, some people collect stamps, Action has high-priced smoking devices.