Sim Lim Square is the destination for most people in the know for bargains on electrical and electronic goods, though it is an absolute minefield there, not for the feint hearted and you have got to bargain very hard. Knowing exactly what you want and how much it costs in say, Harvey Norman as a comparison is a reasonable approach. Since the competition at Sim Lim is so fierce between shops you can get very good prices if you keep cool - there are of course places where you might be able to get things cheaper, but then, you'd end up shopping around and around for ages only to end up saving $10.
Other places to try:
Orchard Road (believe it or not, it is not a total rip off unless you are a 6' 5" Ang Moh).
Funan IT Mall.
Some larger stores can give good competitive prices. Best Denki was the best place that I ended up getting my fridge and washing machine after lots of shopping around.
sometimes these are "export" sets, ie. no guarantee, so they do not have to factor in the additional charges as per "normal" sets.
and again... sometimes the suppliers give them a good price because of their high sales volume. i believe for these kinda sets, they do come with the usual form of guarantee.
and again... (hehe am getting long-winded here), :smt025 i think some sets come in from india la, so the costs for them may be cheaper la!