A dad-of-four set up a cocaine "shop" in his home after losing his job because of the coronavirus pandemic.
Police discovered more than 750g of cocaine and £6,140 in cash when they raided Jamie O'Connor's address.
Liverpool Crown Court heard the drugs could have raked in £75,000 when sold in individual deals on the streets.
O'Connor confessed to police that he had flogged a kilo of cocaine every two weeks since being made redundant last June.
But a judge slammed the Crown Prosecution Service (CPS) over its decision not to charge the 30-year-old over the estimated 20 kilos he claimed to have sold.
Police said there were "a number of people" at his home in Parkhill Road, Birkenhead when they arrived on the evening of April 12 this year.
Michael Stephenson, prosecuting, said O'Connor revealed he had "about a kilo of cocaine" and explained where it could be found.
He said officers found a set of scales and quantities of cocaine, ranging from "four and a half ounce deals down to single deals", which totalled 753.43g and had a potential street value of up to £75,347.
Mr Stephenson said: "He was quite forthcoming in interview. He dealt with his history about being made redundant in June of last year and he said he became involved in the supply of controlled drugs from that date.
"He said he had a number of debts including a drug debt for his own cocaine and cannabis use, he accepted there would be evidence of drug dealing on the phone - although those enquiries haven't been carried out - and he said he was dealing a kilo of cocaine every two weeks for the lads he owed money to, who would deliver it to him, and he would take phone calls and then deal it to others."
O'Connor was originally charged with being concerned in the supply of cocaine - relating to his alleged dealing overall - plus possessing cocaine with intent to supply, possessing cannabis with intent to supply and possessing criminal property.
The CPS accepted guilty pleas to possessing cocaine with intent to supply, simple possession of cannabis, and possessing criminal property, and dropped the other charges.
Judge David Aubrey, QC, said: "So in interview he admitted dealing a kilo of cocaine every two weeks. For how long?"
Mr Stephenson said: "Since June of the previous year." The judge replied: "So a substantial quantity of cocaine."
Referring to the charge of being concerned in the supply of cocaine, Mr Stephenson said a reviewing lawyer "made a conscious decision not to put that on the indictment".
Asked why, he said the CPS lawyer "was of the view that could be reflected in the sentence".
Judge Aubrey said it could not, as it was more than just relevant background information.
"Am I right or am I wrong?" he asked. "You're right, your honour," replied Mr Stephenson.
The judge said he had been making observations about such charging decisions to the CPS since he was appointed in 2005 but "it still doesn't seem to make any difference".
He said he was sentencing O'Connor for 750g of cocaine - a "category three" case with a starting point of four and a half years in prison - instead of 20 kilos, a "category one" case with a starting point of 10 years.
Judge Aubrey said: "This is a classic, graphic illustration of where I believe a reviewing lawyer in truth has not given sufficient consideration to the evidence."
However, he said O'Connor would only be sentenced for what he had pleaded guilty to.
O'Connor, now of Houghton Road, Woodchurch, had two previous convictions, including possessing cannabis in 2007.
Referring to his client's admissions in interview, John Weate, defending, said: "It shows perhaps his criminal naivety."
He suggested it also showed O'Connor had been"exploited" to an extent, although he had been "willing".
Mr Weate said O'Connor had a fiance who had three children he regarded as his step children.
He said: "The plans for the defendant and his fiance to get married have clearly had to be put on hold."
Mr Weate said O'Connor also had a 10-year-old son, with whom he normally had regular contact, but hadn't seen since April.
He said his client had "managed" an addiction to cocaine and debts until he lost his job as a forklift truck driver because of the pandemic and then dealt cocaine to repay his debts.
Mr Weate said O'Connor had struggled with undiagnosed mental health issues that came about after his 33-year-old brother killed himself, and that O'Connor had also "made efforts on his own life".
He said the cash at his home was set aside for his drug suppliers to collect and O'Connor was assaulted last November "by others who wanted to obtain the drugs that were in his possession".
Judge Aubrey said O'Connor was "not an unintelligent man" and he took into account that he was "lightly convicted" with four children, "a good working record" and mental health problems.
He gave him a full third discount off his sentence because of his "extremely frank" admissions, but said when police raided his home they found a "considerable quantity of cocaine" valued "at approximately £75,000".
Judge Aubrey said: "This court has no doubt you were operating a retail shop at your home address.
"I say that because the drugs were ready to go, you had the scales in order to weigh the cocaine... and I'm told there were a number of people at your address. I have no doubt they were customers or potential customers."
He said it was during lockdown and "they should not have been at your address under any circumstances, let alone there to purchase cocaine".
The judge said he also took into account his cocaine addiction, as he jailed O'Connor for four and a half years.
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