Prices of Housing Board shops have shot up over the past three years due to limited supply and investor demand, say agents and analysts.
Rentals have followed suit though the increases have not been as dramatic as resale values.
While rents are not as high as those at suburban malls yet, the increases have squeezed margins for tenants, which are often "mom-and-pop" shops or small and medium-sized enterprises.
Mr George Wong, 32, who runs bubble tea shop Moly Cafe in an HDB retail unit in Toa Payoh, pays his private landlord about $3,800 a month for around 380 sq ft of space - equivalent to half the first storey of a standard HDB retail unit.
He said he has been renting the unit since 2010 and reached an agreement with the landlord to keep the rent from skyrocketing. He said his landlord turned down a $2 million offer recently to buy the shop.
Mr Henry Ong, a real estate agent who has been handling commercial property transactions since 2007, told The Straits Times that rents have been rising in tandem with increasing resale values.
"Most HDB shops islandwide could be rented at $4,000 to $5,000 per month five years ago. Now for that amount you'd get only half a shop."
That translates to as much as around $14 per sq ft a month for centrally located retail shops.
Coffee shops cost slightly more.