For around $70 for an electronic vaporiser, some sellers will throw in free delivery and even a box of three juice pods worth about $25.
Distributors and re-sellers compete aggressively on social media and private message groups to offer a wide array of vaping products.
One popular online message group had about 8,000 advertisements in March last year. By December, the figure had spiked to more than 115,000 advertisements.
But their activities are being watched by the authorities, as well as market researchers like "Eddy" and "Jason", who collect intelligence on illicit products and smuggling syndicates.
Both men, who asked not to be identified, said smuggling and selling e-cigarettes is lucrative because of the fat profit margins.
A box of e-liquid, which has a cost price of $10 to $15 in China, can be smuggled and sold here for between $25 and $30.
Eddy said: "The demand for e-cigarettes could outstrip contraband cigarettes because vaping is a less expensive habit and it is perceived as cooler than cigarette smoking."
Jason said conditions were ripe for contraband syndicates during the Covid-19 movement restrictions and some switched to sneaking in e-vaporisers when the border with Malaysia closed in March last year.
He said: "Compared to contraband cigarettes, a master case of 300 boxes (each containing three pods) of vape juice pods is easier to conceal among other goods than cartons of contraband cigarettes."
The Immigration and Checkpoints Authority (ICA) said there was an increase in the number of attempts to smuggle controlled items into Singapore through low-value goods last year.
Contraband cases detected through low-value goods rose by more than five times from 610 in 2019 to 4,000 last year, the ICA said.
In an e-mail reply to The Sunday Times on Feb 10, the Tobacco Association of Singapore said it was concerned with the relatively easy access to illicit products.
But it applauded the authorities for taking the necessary enforcement action to thwart illicit trade.
Its spokesman said: "This is an issue that has a broad impact on Singapore's tobacco control policies, legitimate businesses and smokers in Singapore. We have been in regular contact with the authorities and are prepared to work with them to tackle illicit trade."
The Health Sciences Authority (HSA) said Singapore adopts a multi-pronged approach to curb the import, sale and possession of e-vaporisers, including public education, counselling and enforcement.
It partners the ICA to interdict prohibited products at checkpoints, and also conducts surveillance and enforcement action against those who buy or sell vaping products online.
From 2018 to last year, HSA carried out more than 170 operations against illegal online sales.
A spokesman said: "To complement our enforcement operations, HSA has also collaborated with online platforms like Instagram, Facebook, and related e-commerce sites, to remove postings on the illegal sale of such products."
Last year, more than 2,000 postings were removed, HSA added.
A Carousell spokesman told ST: "Trust and safety are one of our top priorities and we are committed to ensuring that Carousell remains a safe marketplace for our users.
"As per our listing guidelines, Carousell strictly prohibits the listing of e-vaporisers or e-cigarettes of any kind."
Zaihan Mohamed Yusof