Detectives investigating the murder of Nairn banker Alistair Wilson say the cost of the inquiry has reached £380,000.
Alistair Wilson was gunned down on his doorstep six months ago
A 29-man inquiry team from Northern Constabulary is hunting the lone gunman who killed Mr Wilson on his doorstep on 28 November last year.
Detective Chief Inspector Peter MacPhee said officers would be given all available resources to solve the case.
Police have been unable to establish a motive for the 30-year-old's killing.
Speaking at the six-month point of the murder investigation, Mr MacPhee, the officer leading the inquiry, said costs would rise further.
"The needs of the investigation will receive the appropriate resources," he said.
"We have not included police salaries but the cost is currently over £380,000.
"This includes overtime, the cost of setting up the incident room plus most other day-to-day running costs.
"But we don't have all the invoices in, for example, all the DNA tests and other specific necessities."
About 214 DNA samples and 2,500 statements have been taken during the six months of the murder inquiry.
Mr MacPhee added: "Although there are fewer officers working on the case now, we can draft in the necessary personnel as and when necessary."
Mr Wilson's killer used a Schmeisser semi-automatic pistol, of which about 40,000 were originally manufactured.
The gun is small enough to fit into the palm of a hand and police believe it may have been brought into the UK during or after World War II.
The pistol was found in a drain about half a mile from Mr Wilson's home where he lived with his wife, Veronica, and two sons.