The latest charges include a 32-year-old man, alleged to have coordinated the plot, who was initially arrested in February on unrelated charges.
It takes the total number of people charged so far over the incident to 11.
Police say it was a botched extortion attempt.
The alleged ringleader was initially arrested in Blacktown, in Western Sydney, on February 23.
During a search of the man's car, police seized methylamphetamine and a pistol, and during a subsequent search of a property in Penrith, they seized cannabis and a vehicle.
The man was charged with firearm and drug offences.
Over the course of the investigation, detectives uncovered evidence that the man allegedly coordinated and participated in the kidnapping and murder of Mr Baghsarian, formally arresting him on July 8.
He was charged with murder and kidnapping offences.
On July 9, police arrested a 22-year-old man at Riverstone Police Station and on Monday arrested a 21-year-old man in Lethbridge Park and 19-year-old man at Mt Druitt Police Station.
The 22 year-old man was charged with murder and kidnapping offences.
The 21-year-old and 19-year-old were charged with being accessories to the crimes.
Mr Baghsarian was allegedly taken from his North Ryde home in the early hours of February 13, sparking a major search effort during which police urged his kidnappers to release him.
The grandfather's body was found 11 days after he vanished near a golf club in the semi-rural suburb of Pitt Town in Sydney's north-west.
Police allege the elderly widow was not the intended target of the kidnap-ransom plot.
The 19-year old man is due to face Mount Druitt Local Court on Tuesday, while the 32-year-old alleged ringleader and 22-year-old are both due to appear at Penrith Local Court on Friday.
The 21-year-old man has already appeared in court.
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