Herbert told the court it was a “fictional chat” and said he had no knowledge of 18kg coming into the country at that time.
He said he also obtained bags of cannabis to use in the video for his hit song I’m From.
The musician said buying in bulk also reduced the chance of him coming to the attention of the police as he was often stopped both in London and elsewhere in the country.
The trial was previously told the 24-year-old was a heavy user of cannabis and had supplied socially to others in the music industry including his entourage.
He was also supplying to three people who lived with him at his address in Bracebridge Heath, near Lincoln.
However, prosecutors claim he was involved in commercial transactions of up to 60kg.
Mr Scobie said the artist was selling about 5kg (11lbs) of the Class B drug on a “sporadic” commercial basis – making a small profit of £300-£400 on each deal.
The court heard two sets of weighing scales and a cannabis grinder were recovered from Herbert’s London home on Lonsdale Road in Notting Hill, where he lived with his mother.
Mobile phone footage of the star handling a bag of cannabis and allegedly complaining about the poor quality was played to the judge.
A number of photographs also showed Herbert handling large amounts of cash, the prosecution claimed.
Mr Scobie said Herbert was an internationally recognised musician with a legitimate income and made videos which demonstrated large amounts of cash.
The hearing was adjourned until 31 January when the judge will give his ruling and pass sentencing.
