By Merritt Enright, Nigel Chiwaya and Robin Muccari for NBC News

In a 2018 survey by Americans for Safe Access, more than 25 percent of the 525 respondents said they often go without treatment because they cannot afford medical marijuana in their states. The respondents’ average cost per month ranged from $50 to $1,500.

“I'm paying a lot of money every month in out-of-pocket copays for my medication,” said McClellan, 54. “On top of that, I have to pay ridiculous prices for medical cannabis in the state of Minnesota."

He said he spends about $125 to $150 a month on black market weed. The equivalent product purchased through the state program would cost him about $500, McClellan said.

Some 37 states and the District of Columbia have moved to legalize marijuana for medical use in the last decade. But as McClellan’s case illustrates, the price can be prohibitively expensive for those who rely on the drug to alleviate their chronic pain, nausea and other conditions.

Across the U.S., the price of medical marijuana can be more than double the cost of street pot – even before you factor in the additional step required to keep it legal. Patients have to qualify for a medical marijuana card, which can cost up to $200 a year in states like Minnesota, according to an NBC News review.

“I would say affordability is the number one barrier to access,” said Debbie Churgai, executive director of Americans for Safe Access, a Washington D.C.-based organization that advocates for safe and legal access to medical marijuana.

The cost of the state-issued medical marijuana cards varies widely across the U.S., NBC News found.

In a handful of states, including Utah, Colorado and Missouri, it costs less than $50. New Mexico issues its cards free of charge. But in three states – Minnesota, Arizona and Oregon – it costs at least $150. And in several others, the cards cost between $50 and $100.

The cards must be renewed annually and paid for each year. After obtaining one, the patient must still pay out of pocket for the cannabis products themselves.

“Even if the fee is as low as $25, at the end of the day patients are still paying for medicine that is really, really expensive,” Churgai said.

Advocates point out that no other form of medicine requires patients to pay an annual fee before they can obtain it. But the registration card does play a role in keeping overall costs down, according to Maren Schroeder, policy director of Sensible Change Minnesota, a group dedicated to expanding access for medical marijuana patients in the state.

"There is a cost to administer a state medical cannabis program that has to be borne by someone,” said Schroeder. “If it's not a patient registration fee or a tax, it's going to be an increased price of the product. Anyway you put it, the patients are going to pay for it."

Like the registration cards themselves, the cost of medical marijuana varies widely by state.

In New Jersey, which has among the highest prices in the country, an ounce of medical marijuana costs up to $500. In Michigan, an ounce of marijuana flower costs about $265.

It’s difficult to perform a thorough review of medical cannabis costs by state. While states often track marijuana sales, information on price-per-ounce is not readily available. Costs vary widely across different products and not all states offer the same types. The price also varies based on the number of dispensaries and state tax laws.

In a 2018 survey by Americans for Safe Access, more than 25 percent of the 525 respondents said they often go without treatment because they cannot afford medical marijuana in their states. The respondents’ average cost per month ranged from $50 to $1,500.

Minnesota doesn’t yet offer marijuana flower as part of its program – only THC pills and oils – though that is expected to change in March 2022.

Scott Smith, spokesman for the Minnesota Medical Cannabis program, said his office was aware that some patients were priced out of buying products through the program. But he pointed to a 2019 study commissioned by the Minnesota Department of Health that found its prices were comparable to six other states that were analyzed: Colorado, Michigan, New York, Ohio, Pennsylvania, and Washington.

The study found that the average amount Minnesota patients paid for medical marijuana each month was $316. The study, conducted by consulting firm BerryDunn, calculated the results by analyzing sale records from two marijuana manufacturers over the course of three years.

Smith noted that the manufacturers set the prices – not the state – and that Minnesota offers the registration cards for $50 to people on public assistance.

“People have been accessing marijuana through the illicit market well before medical programs existed,” Smith said. “Until the products are covered by insurance or the industry is well developed, including removing federal barriers that exist for the industry, price will continue to be a problem for many individuals.”

McClellan, who lives in the Minneapolis suburb of Bloomington, has been pushing for access to medical marijuana since 2010. He said that despite its legalization, he’s still in much the same situation he’s been in since he began using marijuana to treat his muscle spasms in 2009.

"When I originally went to the Capitol to work on medical cannabis, we were asking for safe, affordable, legal access to treatment recommended by doctors,” McClellan said.

“It's 10 years later, I'm still asking for the same thing. Patients can't afford it."