Andrea Vaughan-Owen, 42, and her sister Roberta, 37, both of Colwyn Bay deny working tax credit, insurance and mortgage frauds, as well as the attempted VAT fraud.
Mr Lee Karu QC told Caenarfon Crown Court they had been driven by ambition.
But Mr Karu said it was more "Laurel and Hardy of Caernarfon" than Bonnie and Clyde.
Judge Niclas Parry is expected to send the jury to consider their verdicts on Tuesday.
Mr Karu, defending Andrea Vaughan-Owen, said civil servants played the role of "Keystone Cops".
The prosecution accepted that the "left had didn't know what the right hand was doing".
He said nobody stepped in and no-one said "stop, this is rubbish what you are talking.”
This is stupidity gone mad without somebody have a word with them and telling them 'this is nonsense'”
The BBC reported yesterday that in his closing speech to the jury Mr Karu said the sisters were driven by ambition.
"You throw a good mixture of delusion into it, what do you have - two ladies in the dock," he said.
He described the £161m VAT reclaim as "nonsense, deluded, idiotic".
"This is stupidity gone mad without somebody have a word with them and telling them 'this is nonsense.'"
He said the jury should clear his client if they thought she acted honestly "in a mixed up, muddled up way".
It was "much more the Laurel and Hardy of Caernarfon" than Bonnie and Clyde, he added.
Paul Taylor, prosecuting, said the two defendants had "led the high life for years without ever doing anything to deserve it".
It started as a £25,000-a-year tax credits fraud and when the "tap" was turned off they moved into VAT fraud and failed, he said.
"Hopefully systems will be strong enough to stop it happening again."
The sisters became used to "high living" and there was an "almost frenetic interest in money".
"We suggest these people really did expected to get a vast sum of money," he added.
Andrea Vaughan-Owen told the jury she and her sister did not understand the VAT form.
She said the form was filled after a judge, at a house repossession hearing, said they had two hours to complete it.
The prosecution pointed out that the hearing took place in October 2008 and the form was signed in December.
The defendant denied she was changing her evidence.
