I'm only familiar with KL since we stay here.
Anything imported is about same price or more expensive than Singapore, due to import duty tax on many items. So dont't bother about big brand items unless there's a good sale going on.
Locally made items or local brands are probably at better prices, since no GST here.
E.g. Safe and Sound baby latex mattresses and beddings is a good quality local brand.
Bumblebee offer baby mattresses, beddings, dish detergent and many miscellaneous baby items. Quite fine.