His addiction, he said, took a toll on his next business - The Cutting Shed - at the Okara Shopping Centre.
Monk said the $16,280 cash police found in the car he was driving on Riverside Dr on May 18, 2011 was part of proceeds from a Harley Davidson motorcycle he sold in April 2011 for just under $20,000.
On why he ran off into a mangrove swamp and discarded methamphetamine when stopped by police on Riverside Dr, Monk said he was embarrassed about his drug addiction which he kept as a secret.
He said he panicked because his girlfriend believed he wasn't using methamphetamine anymore.
On June 3, 2011, Monk said he arranged to meet and buy methamphetamine from Nicholas Nordstrand at Henwood's workshop on Herekino St where police later arrived.
The pair discussed drug dealing in an upstairs room, Monk said, because they didn't want Henwood to know what they were up to.
"Would you accept that you're the reason why this man (Henwood) is on trial for these serious charges?" asked Henwood's lawyer Wayne McKean.
"Yes I do," Monk replied.
Nordstrand pleaded guilty to a charge of possession of methamphetamine and was sentenced to four years in prison in August 2011.
The jury is expected to go out today after closing submissions.