Cheated clients of the now defunct auction house were "fobbed off" or sent dud cheques, and bank accounts of online bidders were raided, Reading Crown Court was told. Cameo boss Jonathan King even treated himself to a luxury holiday at his victims' expense, said Gordon Menzies, prosecuting.
He added: "It's not just that clients had difficulties and delays in getting their money - many never got paid at all. The 'lucky' ones got a cheque... and, more often than not, it bounced."
One disgruntled client was told a cheque was in the post 20 times, said Mr Menzies. Other customers' goods, such as rare Beatles memorabilia, went missing, never to be seen again, and Mr Menzies said: "You cannot help but wonder whether something more sinister happened to the 'lost' items."
The true scale of the deception may never be known, said Mr Menzies, but could involve up to £250,000.
In the dock beside 63-year-old Mr King, of Mattock Way, Abingdon, Oxfordshire, was his wife Beverley and brother-in-law Glenn Norcliffe, of Marcuse Road, Caterham, Surrey.
The trio deny a total of 11 offences allegedly committed between 2009 and 2012.
Mr Norcliffe denies fraud by abusing his position; Mr King denies fraud and making false statements and his wife denies being concerned in the criminal retention or control of property.
Mr Menzies said customers entrusted goods to Cameo expecting to be paid, minus the firm's 20% commission, once the items were sold. But he added: "That is exactly what was not happening."
Instead, "large round sums, clearly the proceeds of auctions, were appearing in the Kings' bank accounts - other people's money."
Those who complained, jurors heard, would be told a non-existent department in Wiltshire was responsible or that "the cheque writer is at our other office".
Mr Norcliffe even insisted a £10,000 bill had been paid, showing the customer a screen grab of an electronic transfer.
But, said Mr Menzies, Mr Norcliffe had cunningly completed all but the vital last stage of the process in order to generate the appearance of a completed transaction.
Other complainants were met with open hostility or called liars, the court was told.
The Kings regularly paid themselves £5000 per month and Mr Norcliffe took £4000 per month, jurors heard, while clients "went with nothing but empty promises". Mr Menzies said clients' cash also funded a £7000 holiday for the Kings.
He said Mr King would even bid for clients' items at his own auctions - "a clear conflict of interest" - then sell them on at higher prices.
Mr King used a false name to squirrel away the profits in a fund referred to as "Jon's holiday account", jurors were told.
When challenged, the court heard, Mr King insisted he had done nothing wrong, claiming: "Everyone does it."
Eventually, the net began to close around Cameo in early 2012.
But then, said Mr Menzies, "in the last few months of business, something very, very strange started happening".
He said online browsers, who had registered to make bids via credit card, noticed unauthorised sums of money vanishing from their bank accounts and, as the final days of Cameo approached, these instances "rocketed".
Mr Menzies said: "Who benefits? The money went to Jonathan and Beverley King. It allowed them to keep funding their personal and business accounts, and Glenn Norcliffe to keep writing cheques to himself."
Investigators discovered more than £100,000 worth of such fraudulent transactions, the court heard.
When the business finally folded in April 2012, said Mr Menzies, "many people who had consigned goods lost them, and many people owed money lost out".
Mr King was declared bankrupt the following month. But even then, the prosecution allege, his mendacity continued because he falsely told insolvency practitioners he owned no antiques - even as he secretly sold them on eBay. Not only was that a lie, said Mr Menzies, "it's worse, because it was a statutory declaration - it's perjury".
In addition, he said, Mr King used his own children's online accounts to do so, resulting in his daughter being questioned in a police station.
Mr Menzies said: "It says something about a person if they're exposing their children to risk."
As investigators closed in, the court heard, Beverley King declined to answer questions but claimed in a prepared statement she had no knowledge of wrongdoing.
Mr Norcliffe, said Mr Menzies, conceded people were being "fobbed off and lied to" but did so with an air of "breeziness - as if there was nothing wrong with this... he couldn't remember specifics because it happened so often".
Mr Menzies added: "Mr King took a different tack - he says he wasn't aware (of what was going on); that money may have been going into his account; customers may not have been paid but he didn't know anything about it. Well, hang on... it was his business."
The trial, which could last up to six weeks, continues.