I've shopped in Tokyo, London, Paris, Toronto, Australia and the US for groceries and household items. We are more expensive. Period.
NTUC is not a co-operative. It is a Temasek-linked cartel and its practices are highly anti-competitive. If it had operated in America a multi-billion class action anti-trust lawsuit would have been filed right away.
TFBH is right: S'pore being a high-priced place has nothing to do with our having to import essential items. Walmart and Tesco import everything from China, and their prices are at least 40%–70% than comparable items here.
Three factors are at play here:
1. Land pricing. The government is the biggest land owner here. By tendering land parcels at high minimum bid prices, pegging HDB prices to private property, maintaining high commercial rents via JTC and HDB ... the govt has effectively set up a rentier state which sucks money from the people back to the state, its various state-owned corporations and their shareholders, i.e. the cronies and elite . High land prices → high rentals → high business cost and retail prices.
2. Market collusion. The economy – unlike the other 3 dragon economies – is dominated by MNCs and GLCs. So there's market collusion on a grand scale which squeezes out the small proprietor and SMEs. Chain stores dominate, many of which are GIC or Temasek-owned. Result: effective cartels formed with price inflexibility.
3. Unbridled immigration of super-wealthy folks → inflation. You don't need a PhD in economics to understand how this impacts property prices and secondarily retail prices.