Retired IT project manager Brettmann Klaus, 61, thought he had a good deal when he paid $640 for a supposedly brand new Samsung smartphone in 2012.
But he ended up losing $7,000 after falling for a scam that tricks victims into making multiple payments to solve delivery or Customs problems.
Last year, the police received 231 reports of such scams, a big jump from 14 cases in 2012.
Conmen would post online ads of discounted smartphones, tablets and laptops on shopping websites like Gumtree, Craigslist and Locanto as well as social network site Facebook.
They dangled bait like the offer of a Samsung Galaxy SIII smartphone at just $640, which was much cheaper than the market retail price of $998 then.
"The company that advertised on Gumtree looked legitimate; it even had its own website, complete with PayPal and credit card payment options," said Mr Klaus.
He contacted the seller via the e-mail address in the Gumtree advertisement and transferred the payment to a DBS account in June 2012.
Two days later, he received an e-mail ridden with grammar mistakes, which told him of a shipment mix-up and that a package with 12 units of various Apple and Samsung smartphones and tablets worth $9,500 was on its way to him instead.
He was given the choice of paying for all the items at a "discounted" rate of $6,300.
And he paid up, thinking he could recover the cost by reselling them.
"Until today, that shipment has still not arrived," said Mr Klaus, who made a police report in June 2012 after the seller asked for more money to solve problems with the Singapore Customs.
Commenting on the scam, Forrester telco analyst Clement Teo said victims were likely moved by the hope of recouping their losses.
"In-demand electronics goods like Apple and Samsung smartphones are easy to resell," he said.
Police said victims of such scams lost a total of $210,000 last year, 12 times the $17,000 that was lost in 2012.
Individual losses ranged from $70 to $10,600.
Most victims were professionals aged between 20 and 39.
"Money mules" were used to transfer the payments from local bank accounts to overseas ones. They were then offered a cut.
Said Mr Terrence Tang, senior director of consumer at security software firm Trend Micro in Asia-Pacific: "Be wary of sellers asking for wire transfers and money orders. It is very difficult to get your money back once you have transferred it."
Buyers should pay with credit cards or PayPal as these options offer dispute resolution.
Mr Vincent Oh, director of security firm McAfee's South-east Asia and India operations, said one of the tell-tale signs of a scam is the many grammatical mistakes in e-mail and web posts.