Mbuso and other farmers sell a gram of cannabis for about R7.
The cannabis is then smuggled into South Africa and Mozambique where it is typically sold for about 10 times the price.
A former South African cannabis dealer, who used to trade exclusively in Swazi Gold and who spoke to Reuters on condition of anonymity, expressed empathy for the Swazi farmers.
"They're good guys, they produce good product. They know what they're doing and they've been doing it for a long time," he said.
While subsistence farmers like Mbuso worry about their future, a few African governments are waking up to the potential of a legal cannabis industry.
A recent report by market intelligence firm Prohibition Partners has created high hopes of a sector that could be worth up to $7bn (R104bn).
Lesotho became the first country in Africa to legalise the production of marijuana for medical use last year. Zimbabwe has followed suit.
The UN reports that more than 10,000 tons of cannabis is produced in Africa every year.