Ben Milstein is a 22-year-old art collector who deals exclusively in marijuana pipes and bongs.

His collection includes more than 500 pieces, ranging in price from $5,000 to $300,000.

Milstein hopes to change the stigma around marijuana by elevating drug paraphernalia as fine art.

Ben Milstein, 22, isn't a typical dealer in the fast-growing marijuana industry.

The up-and-coming art dealer makes a living selling high-end marijuana paraphernalia, including hand-blown glass pipes and bongs, with price tags that run up to six figures.

His company, Grey Space Art, hosts pop-up galleries in major cities like New York, Los Angeles, and Miami, where enthusiasts can buy these sculptural works. In two years, his collection has grown to include more than 500 pieces made by roughly 80 artists.

Ben Milstein, left, is a 22-year-old art collector that deals exclusively in marijuana pipes and bongs. Grey Space Art While Milstein said he doesn't consider the gig a full-time job, he has sold about $350,000 in bongs since May. His private collection, which he said he will never liquidate because it demands "to be seen by more people," has at least tripled in value over the last two years.

"There's a reason why I'm in this industry and not buying wall art. It's about the momentum of the cannabis industry," Milstein told Business Insider.

Milstein's success at an age when he's barely old enough to buy marijuana in states where it's legal (you must be 21 or older) demonstrates the wide range of opportunities available to entrepreneurs in the fledgling marijuana industry. He's carving a niche in the club of elite sophisticates that is the art world.

"I'm not selling bongs — I'm selling works of art," Milstein told us earlier this year.

Milstein graduated high school a semester early and looked to the marijuana industry for investment opportunities. A friend tipped him off about cannabis stocks in 2013, two weeks before the drug became legal in Colorado. The stocks exploded, according to Milstein.

He worked for a brief stint at an advertising and branding agency before eventually embarking on a journey around the world to find and buy glass pipes and bongs. He worked under the pseudonym "Mr. Grey," because selling drug paraphernalia is illegal under federal law.

Elaborate marijuana pipes and bongs sit on display in a chest in Milstein's New York City apartment. Grey Art

"I'm in the emerging art world. Buying the best work does not come at a super high price," Milstein said. "Having made a little bit of money, I could buy all the best pieces."

His elaborate pipes and bongs range in price from $5,000 to $300,000. A piece called "Hayabusa Satellite" (priced at $110,000) lets users inhale marijuana smoke from the base of a spacecraft-replica. A charming "Honeybear," which looks like the classic honey dispenser, went up in value from $100 to $5,000 before Milstein scooped it up two years ago.

The sculptures are all handmade from borosilicate glass, a material known as a hard glass. The artist typically uses a high-powered torch and spins different colored glass rods in the flame.

"Hayabusa Satellite." Grey Art

Milstein launched Grey Space Art in 2016, throwing a launch party at the New York City home of Italian fashion designer Riccardo Tisci. He's since taken his collection on the road to Art Wyndwood art fair, New York Fashion Week, and the Chateau Marmont hotel in Hollywood.

The art collector recently moved from New York to Los Angeles, where he hopes to elevate the perception of drug paraphernalia as fine art. The timing works out. Californians voted to legalize recreational marijuana last year, and sales of the drug are expected to begin in 2018.

Milstein said he couldn't do what he does at any other point in history.

"I'm in full support of legalization and removing the stigma around marijuana. That starts with showcasing these artists as professionals," Milstein added.