Singapore is no longer the shoppers' haven it used to be reputed for!
Even duty-free is not really so except for alcohol/cigarettes and perfumes.
The last time I was there the camera shop assistant told me I should shop in Australia if I found that their prices were the same as is Australia; which is fair enough and thus I bought all my Canon gear here in Perth and enjoy local support/service and warranty...
HTH
Cheers
Bill